Reviewed, UniProtKB/Swiss-Prot O23680 (TOC33_ARATH)

Names and origin

Protein names

Recommended name:
    Translocase of chloroplast 33, chloroplastic
      Short name=AtToc33
    EC=3.6.5.-
Alternative name(s):
    33 kDa chloroplast outer envelope protein
    Plastid protein import 1

Gene names

Name:	TOC33
Synonyms:	PPI1
Ordered Locus Names:	At1g02280
ORF Names:	T7I23.11

Organism

Arabidopsis thaliana (Mouse-ear cress) [Complete proteome]

Taxonomic identifier

3702 [NCBI]

Taxonomic lineage

Eukaryota › Viridiplantae › Streptophyta › Embryophyta › Tracheophyta › Spermatophyta › Magnoliophyta › eudicotyledons › core eudicotyledons › rosids › eurosids II › Brassicales › Brassicaceae › Arabidopsis

Protein attributes

Sequence length	297 AA.
Sequence status	Complete.
Sequence processing	The displayed sequence is not processed.
Protein existence	Evidence at protein level.

General annotation (Comments)

Function	GTPase involved in protein precursor import into chloroplasts. Seems to recognize chloroplast-destined precursor proteins and regulate their presentation to the translocation channel through GTP hydrolysis. Binds GTP, GDP, XTP, but not ATP. Probably specialized in the import of nuclear encoded photosynthetic preproteins from the cytoplasm to the chloroplast, especially during early development stages. Ref.6 Ref.8 Ref.9 Ref.10 Ref.11 Ref.13 Ref.15 Ref.16 Ref.17 Ref.18
Cofactor	Binds 1 magnesium ion by subunit.
Subunit structure	Homodimer, heterodimer with TOC34 and TOC159, and monomer. The homodimerization and the dimerization with TOC159 require the binding of GTP on Arg-130, and an hypothetical coGAP factor. The dimeric form has a higher GTPase activity than the monomeric form. Part of the TOC core complex that includes 1 protein for the specific recognition of transit peptides surrounded by a ring composed of four proteins forming translocation channels, and four to five GTP-binding proteins providing energy. This core complex can interact with components of the TIC complex to form a larger import complex. Chloroplastic protein precursor such as prSS (precursor of the RuBisCO small subunit) interacts with these complexes. The TOC complex contains a specific subset of polar lipids such as digalactosyldiacylglyceride (DGDG), phosphatidylcholine (PC) and phosphatidylglycerol (PG). Interacts at least with TOC75-3. Ref.8 Ref.10 Ref.11 Ref.1 Ref.7 Ref.20 Ref.21 Ref.22
Subcellular location	Plastid › chloroplast outer membrane; Single-pass membrane protein. Note: May contains beta barrel transmembrane regions. Ref.11 Ref.1 Ref.12 Ref.14
Tissue specificity	Mostly expressed in seedlings and flowers, and, to a lower extent, in roots, stems, and leaves. Ref.13 Ref.1
Developmental stage	Mostly expressed in photosynthetic tissues undergoing rapid growth. Observed in cotyledons and vascular tissues of hypocotyls of young seedling. In roots, restricted to apical and lateral meristems, and vascular bundles. In stems, mostly detected in the upper part. Expressed in young and middle-aged leaves. In flowers, confined to sepals. Ref.13 Ref.1
Induction	Up-regulated by CIA2 in leaves. Induced in light but repressed in darkness. Ref.13 Ref.5
Post-translational modification	Phosphorylated by a kinase present in the outer envelope of chloroplast. When ser-181 is phosphorylated, the binding to preprotein, GTP and GDP is inhibited, and thus, GTPase activity is repressed. Ref.8 Ref.16 Ref.18
Disruption phenotype	Plants exhibits a pale yellowish phenotype. Ref.6 Ref.13 Ref.1
Sequence similarities	Belongs to the TOC34 family.
Biophysicochemical properties	Kinetic parameters: KM=290 nM for GDP (at pH 7.4) KM=5.7 µM for GTP (at pH 7.6 and 25 degrees Celsius) Vmax=1040 nmol/min/µg enzyme with GTP as substrate (at pH 7.4)

Ontologies

Keywords
Biological process	Protein transport Transport
Cellular component	Chloroplast Membrane Plastid Plastid outer membrane
Domain	Transmembrane
Ligand	GTP-binding Magnesium Metal-binding Nucleotide-binding
Molecular function	Hydrolase Receptor
PTM	Phosphoprotein
Technical term	3D-structure Complete proteome
Gene Ontology (GO)
Biological process	protein targeting to chloroplast Traceable author statement. Source: TAIR
Cellular component	chloroplast outer membrane Ref.1 Inferred from direct assay. Source: TAIR integral to membrane Inferred from electronic annotation. Source: UniProtKB-SubCell
Molecular function	GTP binding Ref.9 Inferred from direct assay. Source: TAIR GTPase activity Ref.9 Inferred from direct assay. Source: TAIR P-P-bond-hydrolysis-driven protein transmembrane transporter activity Inferred from electronic annotation. Source: InterPro identical protein binding Ref.10 Inferred from physical interaction. Source: IntAct magnesium ion binding Inferred from electronic annotation. Source: UniProtKB-KW receptor activity Inferred from electronic annotation. Source: UniProtKB-KW
Complete GO annotation...

Binary interactions

With	Entry	#Exp.	IntAct	Notes
itself		1	EBI-639377,EBI-639377
CPK11	Q39016	4	EBI-639377,EBI-979321
CPK4	Q38869	3	EBI-639377,EBI-979475
TOC159	O81283	1	EBI-639377,EBI-639063

Sequence annotation (Features)

Feature key

Position(s)

Length

Description

Graphical view

Feature identifier

Molecule processing

Chain

1 – 297

297

Translocase of chloroplast 33, chloroplastic

PRO_0000352655

Regions

Transmembrane

37 – 53

17

Potential

Nucleotide binding

46 – 51

6

GTP

Nucleotide binding

65 – 70

6

GTP

Nucleotide binding

208 – 209

2

GTP

Region

65 – 68

4

Homodimerization By similarity

Region

125 – 130

6

Homodimerization

Sites

Metal binding

50

1

Magnesium

Metal binding

68

1

Magnesium

Binding site

160

1

GTP; via amide nitrogen

Amino acid modifications

Modified residue

181

1

Phosphoserine Ref.8 Ref.16 Ref.18

Experimental info

Mutagenesis

45 – 50

6

GGVGKS → RGVGNR: Reduced GTPase activity and impaired interaction with TOC159. Ref.11

Mutagenesis

130

1

R → A: Loss of homidimerization and heterodimerization with TOC159, reduction of GTPase activity. Ref.10 Ref.20 Ref.21

Mutagenesis

170

1

S → A: Normal phosphorylation. Ref.8

Mutagenesis

175

1

S → A: Normal phosphorylation. Ref.8

Mutagenesis

181

1

S → A: Loss of phosphorylation, normal activity. Ref.8 Ref.16

Mutagenesis

181

1

S → D or E: According to PubMed:16412428, supposed to mimic the effects of phosphoserine, but normal activity. Ref.8 Ref.16

Mutagenesis

181

1

S → T: Phosphothreonine instead of phosphoserine. Ref.8 Ref.16

Mutagenesis

190

1

S → A: Normal phosphorylation. Ref.8

Mutagenesis

200

1

S → A: Normal phosphorylation. Ref.8

Mutagenesis

208

1

E → Q: Normal GTPase activity, but weaker nucleotide binding. Ref.9

Mutagenesis

217

1

D → N: Normal GTPase activity. Ref.9

Mutagenesis

219

1

D → N: Normal GTPase activity. Ref.9

Mutagenesis

220

1

E → Q: Normal GTPase activity. Ref.9

Sequence conflict

147

1

G → A in AAK68809. Ref.3

Secondary structure

1

.

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.

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.

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.

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297

Helix Strand Turn

Details...

Helix

16 – 25

10

Helix

30 – 32

3

Beta strand

36 – 42

7

Helix

50 – 56

7

Beta strand

75 – 80

6

Beta strand

85 – 90

6

Helix

102 – 108

7

Beta strand

119 – 127

9

Helix

133 – 145

13

Helix

149 – 153

5

Beta strand

154 – 159

6

Helix

171 – 187

17

Helix

194 – 200

7

Beta strand

203 – 206

4

Helix

229 – 241

13

Sequences

	Sequence		Length	Mass (Da)
	O23680-1 [UniParc]. Last modified January 1, 1998. Version 1. Checksum: E48892E123BA412D	FASTA	297	32,925
	10 20 30 40 50 60 MGSLVREWVG FQQFPAATQE KLIEFFGKLK QKDMNSMTVL VLGKGGVGKS STVNSLIGEQ 70 80 90 100 110 120 VVRVSPFQAE GLRPVMVSRT MGGFTINIID TPGLVEAGYV NHQALELIKG FLVNRTIDVL 130 140 150 160 170 180 LYVDRLDVYR VDELDKQVVI AITQTFGKEI WCKTLLVLTH AQFSPPDELS YETFSSKRSD 190 200 210 220 230 240 SLLKTIRAGS KMRKQEFEDS AIAVVYAENS GRCSKNDKDE KALPNGEAWI PNLVKAITDV 250 260 270 280 290 ATNQRKAIHV DKKMVDGSYS DDKGKKLIPL IIGAQYLIVK MIQGAIRNDI KTSGKPL

References

	« Hide 'large scale' referencesShow 'large scale' references »
[1]	"Functional analysis of the two Arabidopsis homologues of Toc34, a component of the chloroplast protein import apparatus." Gutensohn M., Schulz B.I., Nicolay P., Fluegge U.-I. Plant J. 23:771-783(2000) [PubMed: 10998188] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [MRNA], CHARACTERIZATION, DISRUPTION PHENOTYPE, SUBCELLULAR LOCATION, TISSUE SPECIFICITY, DEVELOPMENTAL STAGE, INTERACTION WITH TOC75. Strain: cv. Columbia. Tissue: Etiolated seedling.
[2]	"Sequence and analysis of chromosome 1 of the plant Arabidopsis thaliana." Theologis A., Ecker J.R., Palm C.J., Federspiel N.A., Kaul S., White O., Alonso J., Altafi H., Araujo R., Bowman C.L., Brooks S.Y., Buehler E., Chan A., Chao Q., Chen H., Cheuk R.F., Chin C.W., Chung M.K. , Conn L., Conway A.B., Conway A.R., Creasy T.H., Dewar K., Dunn P., Etgu P., Feldblyum T.V., Feng J.-D., Fong B., Fujii C.Y., Gill J.E., Goldsmith A.D., Haas B., Hansen N.F., Hughes B., Huizar L., Hunter J.L., Jenkins J., Johnson-Hopson C., Khan S., Khaykin E., Kim C.J., Koo H.L., Kremenetskaia I., Kurtz D.B., Kwan A., Lam B., Langin-Hooper S., Lee A., Lee J.M., Lenz C.A., Li J.H., Li Y.-P., Lin X., Liu S.X., Liu Z.A., Luros J.S., Maiti R., Marziali A., Militscher J., Miranda M., Nguyen M., Nierman W.C., Osborne B.I., Pai G., Peterson J., Pham P.K., Rizzo M., Rooney T., Rowley D., Sakano H., Salzberg S.L., Schwartz J.R., Shinn P., Southwick A.M., Sun H., Tallon L.J., Tambunga G., Toriumi M.J., Town C.D., Utterback T., Van Aken S., Vaysberg M., Vysotskaia V.S., Walker M., Wu D., Yu G., Fraser C.M., Venter J.C., Davis R.W. Nature 408:816-820(2000) [PubMed: 11130712] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA]. Strain: cv. Columbia.
[3]	"Empirical analysis of transcriptional activity in the Arabidopsis genome." Yamada K., Lim J., Dale J.M., Chen H., Shinn P., Palm C.J., Southwick A.M., Wu H.C., Kim C.J., Nguyen M., Pham P.K., Cheuk R.F., Karlin-Newmann G., Liu S.X., Lam B., Sakano H., Wu T., Yu G. , Miranda M., Quach H.L., Tripp M., Chang C.H., Lee J.M., Toriumi M.J., Chan M.M., Tang C.C., Onodera C.S., Deng J.M., Akiyama K., Ansari Y., Arakawa T., Banh J., Banno F., Bowser L., Brooks S.Y., Carninci P., Chao Q., Choy N., Enju A., Goldsmith A.D., Gurjal M., Hansen N.F., Hayashizaki Y., Johnson-Hopson C., Hsuan V.W., Iida K., Karnes M., Khan S., Koesema E., Ishida J., Jiang P.X., Jones T., Kawai J., Kamiya A., Meyers C., Nakajima M., Narusaka M., Seki M., Sakurai T., Satou M., Tamse R., Vaysberg M., Wallender E.K., Wong C., Yamamura Y., Yuan S., Shinozaki K., Davis R.W., Theologis A., Ecker J.R. Science 302:842-846(2003) [PubMed: 14593172] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA]. Strain: cv. Columbia.
[4]	"Arabidopsis ORF clones." Shinn P., Chen H., Kim C.J., Quinitio C., Ecker J.R. Submitted (JUN-2006) to the EMBL/GenBank/DDBJ databases Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA]. Strain: cv. Columbia.
[5]	"Leaf-specific upregulation of chloroplast translocon genes by a CCT motif-containing protein, CIA2." Sun C.-W., Chen L.-J., Lin L.-C., Li H.-M. Plant Cell 13:2053-2061(2001) [PubMed: 11549763] [Abstract] Cited for: INDUCTION.
[6]	"Chloroplast protein translocon components atToc159 and atToc33 are not essential for chloroplast biogenesis in guard cells and root cells." Yu T.-S., Li H.-M. Plant Physiol. 127:90-96(2001) [PubMed: 11553737] [Abstract] Cited for: FUNCTION, DISRUPTION PHENOTYPE.
[7]	"The targeting of the atToc159 preprotein receptor to the chloroplast outer membrane is mediated by its GTPase domain and is regulated by GTP." Smith M.D., Hiltbrunner A., Kessler F., Schnell D.J. J. Cell Biol. 159:833-843(2002) [PubMed: 12473690] [Abstract] Cited for: INTERACTION WITH TOC159.
[8]	"Two Toc34 homologues with different properties." Jelic M., Soll J., Schleiff E. Biochemistry 42:5906-5916(2003) [PubMed: 12741849] [Abstract] Cited for: FUNCTION, BIOPHYSICOCHEMICAL PROPERTIES, PHOSPHORYLATION AT SER-181, DIMERIZATION WITH TOC34, MUTAGENESIS OF SER-170; SER-175; SER-181; SER-190 AND SER-200.
[9]	"Unusual nucleotide-binding properties of the chloroplast protein import receptor, atToc33." Aronsson H., Combe J., Jarvis P. FEBS Lett. 544:79-85(2003) [PubMed: 12782294] [Abstract] Cited for: FUNCTION, MUTAGENESIS OF GLU-208; ASP-217; ASP-219 AND GLU-220.
[10]	"Dimerization of Toc-GTPases at the chloroplast protein import machinery." Weibel P., Hiltbrunner A., Brand L., Kessler F. J. Biol. Chem. 278:37321-37329(2003) [PubMed: 12869544] [Abstract] Cited for: FUNCTION, DIMERIZATION WITH TOC159, MUTAGENESIS OF ARG-130.
[11]	"The roles of Toc34 and Toc75 in targeting the Toc159 preprotein receptor to chloroplasts." Wallas T.R., Smith M.D., Sanchez-Nieto S., Schnell D.J. J. Biol. Chem. 278:44289-44297(2003) [PubMed: 12951325] [Abstract] Cited for: FUNCTION, SUBCELLULAR LOCATION, MUTAGENESIS OF 45-GLY--SER-50, INTERACTION WITH TOC159.
[12]	"Proteomic study of the Arabidopsis thaliana chloroplastic envelope membrane utilizing alternatives to traditional two-dimensional electrophoresis." Froehlich J.E., Wilkerson C.G., Ray W.K., McAndrew R.S., Osteryoung K.W., Gage D.A., Phinney B.S. J. Proteome Res. 2:413-425(2003) [PubMed: 12938931] [Abstract] Cited for: SUBCELLULAR LOCATION, IDENTIFICATION BY MASS SPECTROMETRY.
[13]	"The Arabidopsis ppi1 mutant is specifically defective in the expression, chloroplast import, and accumulation of photosynthetic proteins." Kubis S., Baldwin A., Patel R., Razzaq A., Dupree P., Lilley K., Kurth J., Leister D., Jarvis P. Plant Cell 15:1859-1871(2003) [PubMed: 12897258] [Abstract] Cited for: FUNCTION, DISRUPTION PHENOTYPE, TISSUE SPECIFICITY, INDUCTION BY LIGHT, DEVELOPMENTAL STAGE.
[14]	"Proteomics of the chloroplast envelope membranes from Arabidopsis thaliana." Ferro M., Salvi D., Brugiere S., Miras S., Kowalski S., Louwagie M., Garin J., Joyard J., Rolland N. Mol. Cell. Proteomics 2:325-345(2003) [PubMed: 12766230] [Abstract] Cited for: SUBCELLULAR LOCATION, IDENTIFICATION BY MASS SPECTROMETRY.
[15]	"An outer envelope membrane component of the plastid protein import apparatus plays an essential role in Arabidopsis." Constan D., Patel R., Keegstra K., Jarvis P. Plant J. 38:93-106(2004) [PubMed: 15053763] [Abstract] Cited for: FUNCTION.
[16]	"In vivo assessment of the significance of phosphorylation of the Arabidopsis chloroplast protein import receptor, atToc33." Aronsson H., Combe J., Patel R., Jarvis P. FEBS Lett. 580:649-655(2006) [PubMed: 16412428] [Abstract] Cited for: FUNCTION, PHOSPHORYLATION AT SER-181, MUTAGENESIS OF SER-181.
[17]	"Deletion of core components of the plastid protein import machinery causes differential arrest of embryo development in Arabidopsis thaliana." Hust B., Gutensohn M. Plant Biol. 8:18-30(2006) [PubMed: 16435266] [Abstract] Cited for: FUNCTION.
[18]	"Phospho-mimicry mutant of atToc33 affects early development of Arabidopsis thaliana." Oreb M., Zoryan M., Vojta A., Maier U.G., Eichacker L.A., Schleiff E. FEBS Lett. 581:5945-5951(2007) [PubMed: 18054337] [Abstract] Cited for: FUNCTION, PHOSPHORYLATION AT SER-181.
[19]	"In vitro comparative kinetic analysis of the chloroplast Toc GTPases." Reddick L.E., Vaughn M.D., Wright S.J., Campbell I.M., Bruce B.D. J. Biol. Chem. 282:11410-11426(2007) [PubMed: 17261588] [Abstract] Cited for: BIOPHYSICOCHEMICAL PROPERTIES.
[20]	"Dimerization is important for the GTPase activity of chloroplast translocon components atToc33 and psToc159." Yeh Y.-H., Kesavulu M.M., Li H.-M., Wu S.-Z., Sun Y.-J., Konozy E.H.E., Hsiao C.-D. J. Biol. Chem. 282:13845-13853(2007) [PubMed: 17337454] [Abstract] Cited for: X-RAY CRYSTALLOGRAPHY (3.2 ANGSTROMS) OF 2-250 IN COMPLEX WITH GDP AND MAGNESIUM, DIMERIZATION, MUTAGENESIS OF ARG-130.
[21]	"On the significance of Toc-GTPase homodimers." Koenig P., Oreb M., Rippe K., Muhle-Goll C., Sinning I., Schleiff E., Tews I. J. Biol. Chem. 283:23104-23112(2008) [PubMed: 18541539] [Abstract] Cited for: X-RAY CRYSTALLOGRAPHY (1.96 ANGSTROMS) OF 1-251 IN COMPLEX WITH GDP AND MAGNESIUM, DIMERIZATION, MUTAGENESIS OF ARG-130.
[22]	"The GTPase cycle of the chloroplast import receptors Toc33/Toc34: implications from monomeric and dimeric structures." Koenig P., Oreb M., Hoefle A., Kaltofen S., Rippe K., Sinning I., Schleiff E., Tews I. Structure 16:585-596(2008) [PubMed: 18400179] [Abstract] Cited for: X-RAY CRYSTALLOGRAPHY (2.85 ANGSTROMS) OF 1-251 IN COMPLEX WITH GDP; GNP AND MAGNESIUM, DIMERIZATION.
+	Additional computationally mapped references.

Cross-references

Sequence databases

EMBLGenBankDDBJ

AJ010724 mRNA. Translation: CAC17698.1.
U89959 Genomic DNA. Translation: AAC24375.1.
AY042869 mRNA. Translation: AAK68809.1.
AY056448 mRNA. Translation: AAL08304.1.
BT025654 mRNA. Translation: ABF74715.1.

IPI

IPI00524670.

RefSeq

NP_001117215.1.
NP_171730.1.

UniGene

At.10710

3D structure databases

PDBPDBe

Entry	Method	Resolution (Å)	Chain	Positions	PDBsum
2J3E	X-ray	3.20	A	2-250	[»]
3BB3	X-ray	2.94	A	1-251	[»]
3BB4	X-ray	2.85	A	1-251	[»]
3DEF	X-ray	1.96	A	1-251	[»]

ModBase

Search...

Protein-protein interaction databases

IntAct

O23680. 10 interactions.

STRING

O23680.

Proteomic databases

PRIDE

O23680.

ProMEX

O23680.

Genome annotation databases

GeneID

839248.

GenomeReviews

Gene locus AT1G02280 in contig CT485782_GR.

KEGG

ath:AT1G02280.

NMPDR

fig|3702.1.peg.346.

Organism-specific databases

TAIR

At1g02280.

Phylogenomic databases

OMA

CARRSEA

Gene expression databases

Genevestigator

O23680.

Family and domain databases

InterPro

IPR006703. AIG1.
IPR005688. Toc34.
[Graphical view]

Pfam

PF04548. AIG1. 1 hit.
[Graphical view]

PIRSF

PIRSF038134. Toc34. 1 hit.

TIGRFAMs

TIGR00991. 3a0901s02IAP34. 1 hit.

ProtoNet

Search...

Entry information

Entry name

TOC33_ARATH

Accession

Primary (citable) accession number: O23680
Secondary accession number(s): Q94B42, Q9GDD3

Entry history

Integrated into UniProtKB/Swiss-Prot:	October 14, 2008
Last sequence update:	January 1, 1998
Last modified:	November 3, 2009
This is version 62 of the entry and version 1 of the sequence. [Complete history]

Entry status

Reviewed (UniProtKB/Swiss-Prot)

Annotation project

PPAP (Plant Proteome Annotation Project)