Reviewed, UniProtKB/Swiss-Prot O81852 (AKH2_ARATH)

Names and origin

Protein names

Recommended name:
    Bifunctional aspartokinase/homoserine dehydrogenase 2, chloroplastic
      Short name(s)=AK-HSDH 2, AK-HD 2
Alternative name(s):
    Beta-aspartyl phosphate homoserine 2
Including 2 domains:
  Recommended name:
      Aspartokinase
      EC=2.7.2.4
  Recommended name:
      Homoserine dehydrogenase
      EC=1.1.1.3

Gene names

Name:	AKHSDH2
Synonyms:	AK-HSDH II
Ordered Locus Names:	At4g19710
ORF Names:	T16H5.70

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	916 AA.
Sequence status	Complete.
Sequence processing	The displayed sequence is further processed into a mature form.
Protein existence	Evidence at protein level.

General annotation (Comments)

Catalytic activity	L-homoserine + NAD(P)(+) = L-aspartate 4-semialdehyde + NAD(P)H. ATP + L-aspartate = ADP + 4-phospho-L-aspartate.
Enzyme regulation	Threonine interaction with Gln-443 leads to inhibition of aspartate kinase activity and facilitates the binding of a second threonine on Gln-524, leading to a partial inhibition of homoserine dehydrogenase activity (25% of activity remaining at saturation with threonine). Homoserine dehydrogenase activity is also partially inhibited by cysteine (15% of activity remaining at saturation with cysteine). No synergy between threonine and cysteine for the inhibition. 13-fold activation of aspartate kinase activity by cysteine, isoleucine, valine, serine and alanine at 2.5 mM and 4-fold activation by leucine at 2.5 mM, but no activation of homoserine dehydrogenase activity.
Pathway	Amino-acid biosynthesis; L-lysine biosynthesis via DAP pathway; tetrahydrodipicolinate from L-aspartate: step 1/4. Amino-acid biosynthesis; L-methionine biosynthesis via de novo pathway; L-homoserine from L-aspartate: step 1/3. Amino-acid biosynthesis; L-methionine biosynthesis via de novo pathway; L-homoserine from L-aspartate: step 3/3. Amino-acid biosynthesis; L-threonine biosynthesis; L-threonine from L-aspartate: step 1/5. Amino-acid biosynthesis; L-threonine biosynthesis; L-threonine from L-aspartate: step 3/5.
Subunit structure	Homo- or heterodimer Potential.
Subcellular location	Plastid › chloroplast.
Sequence similarities	In the N-terminal section; belongs to the aspartokinase family. In the C-terminal section; belongs to the homoserine dehydrogenase family. Contains 2 ACT domains.
Biophysicochemical properties	Kinetic parameters: KM=11.6 mM for aspartate for the aspartokinase activity (in the presence of 40 mM ATP) KM=6.15 mM for aspartate for the aspartokinase activity (at pH 8.0, in the presence of 200 µM NADPH and 20 mM ATP) KM=1.5 mM for aspartate for the aspartokinase activity (at pH 8.0, in the presence of 200 µM NADPH, 20 mM ATP and a saturating concentration of alanine) KM=26.4 mM for aspartate for the aspartokinase activity (in the presence of 100 mM ATP and 0.5 mM threonine) KM=5.5 mM for ATP for the aspartokinase activity (in the presence of 50 mM aspartate) KM=2.2 mM for ATP for the aspartokinase activity (at pH 8.0, in the presence of 200 µM NADPH and 50 mM aspartate) KM=0.42 mM for ATP for the aspartokinase activity (at pH 8.0, in the presence of 200 µM NADPH, 50 mM aspartate and a saturating concentration of alanine) KM=5.2 mM for homoserine for the reverse reaction of the homoserine dehydrogenase activity (in the presence of 1 mM NADP) KM=1.4 mM for aspartate semialdehyde for the forward reaction of the homoserine dehydrogenase activity (in the presence of NADPH) KM=311 µM for aspartate semialdehyde for the forward reaction of the homoserine dehydrogenase activity (at pH 8.0, in the presence of 150 mM KCl and 200 µM NADPH) KM=24.5 mM for homoserine for the reverse reaction of the homoserine dehydrogenase activity (in the presence of 1 mM NADP and 60 mM threonine) KM=166.1 µM for NADP for the reverse reaction of the homoserine dehydrogenase activity (in the presence of 50 mM homoserine) KM=676.1 µM for NADP for the reverse reaction of the homoserine dehydrogenase activity (in the presence of 100 mM homoserine and 60 mM threonine) Vmax=5.4 µmol/min/mg enzyme toward aspartylhydroxamate for the aspartokinase activity Vmax=165 µmol/min/mg enzyme toward aspartate semialdehyde for the forward reaction of the homoserine dehydrogenase activity Vmax=18.8 µmol/min/mg enzyme toward NADPH for the reverse reaction of the homoserine dehydrogenase activity

Ontologies

Keywords
Biological process	Amino-acid biosynthesis Methionine biosynthesis
Cellular component	Chloroplast Plastid
Coding sequence diversity	Alternative splicing
Domain	Repeat Transit peptide
Ligand	NADP
Molecular function	Kinase Oxidoreductase Transferase
Technical term	Complete proteome Multifunctional enzyme
Gene Ontology (GO)
Molecular function	aspartate kinase activity Ref.5 Inferred from direct assay. Source: TAIR homoserine dehydrogenase activity Ref.5 Inferred from direct assay. Source: TAIR
Complete GO annotation...

Alternative products

This entry describes 2 isoforms produced by alternative splicing. [Align] [Select]

Isoform 1 (identifier: O81852-1)

This isoform has been chosen as the 'canonical' sequence. All positional information in this entry refers to it. This is also the sequence that appears in the downloadable versions of the entry.

Isoform 2 (identifier: O81852-2)

The sequence of this isoform differs from the canonical sequence as follows:
     837-916: LRYVGVVDAV...RLASYLGAPS → RLFTTNVFPFDQCDHILTIYICM

Notes: Derived from EST data. No experimental confirmation available.

Sequence annotation (Features)

	Feature key	Position(s)	Length	Description	Graphical view
Molecule processing
	Transit peptide	1 – 87	87	Chloroplast Potential
	Chain	88 – 916	829	Bifunctional aspartokinase/homoserine dehydrogenase 2, chloroplastic
Regions
	Domain	408 – 476	69	ACT 1
	Domain	492 – 559	68	ACT 2
	Nucleotide binding	564 – 569	6	NADP Potential
	Region	88 – 336	249	Aspartokinase By similarity
	Region	337 – 562	226	Interface By similarity
	Region	563 – 916	354	Homoserine dehydrogenase By similarity
Natural variations
	Alternative sequence	837 – 916	80	LRYVG…LGAPS → RLFTTNVFPFDQCDHILTIY ICM in isoform 2.
Experimental info
	Mutagenesis	441	1	I → A: Loss of threonine sensitivity for the aspartokinase activity and decreased inhibition of homoserine dehydrogenase activity by threonine
	Mutagenesis	443	1	Q → A: Loss of threonine sensitivity for the aspartokinase activity and decreased inhibition of homoserine dehydrogenase activity by threonine
	Mutagenesis	522	1	I → A: No effect on the inhibition of aspartokinase activity by threonine, but decreased inhibition of homoserine dehydrogenase activity by threonine
	Mutagenesis	524	1	Q → A: No effect on the inhibition of aspartokinase activity by threonine, but decreased inhibition of homoserine dehydrogenase activity by threonine

Sequences

	Sequence		Length	Mass (Da)
	Isoform 1 [UniParc]. Last modified November 1, 1998. Version 1. Checksum: 7ECD984DAFC97C4F	FASTA	916	100,250
	10 20 30 40 50 60 MATLKPSFTV SPPNSNPIRF GSFPPQCFLR VPKPRRLILP RFRKTTGGGG GLIRCELPDF 70 80 90 100 110 120 HLSATATTVS GVSTVNLVDQ VQIPKGEMWS VHKFGGTCVG NSQRIRNVAE VIINDNSERK 130 140 150 160 170 180 LVVVSAMSKV TDMMYDLIRK AQSRDDSYLS ALEAVLEKHR LTARDLLDGD DLASFLSHLH 190 200 210 220 230 240 NDISNLKAML RAIYIAGHAS ESFSDFVAGH GELWSAQMLS YVVRKTGLEC KWMDTRDVLI 250 260 270 280 290 300 VNPTSSNQVD PDFGESEKRL DKWFSLNPSK IIIATGFIAS TPQNIPTTLK RDGSDFSAAI 310 320 330 340 350 360 MGALLRARQV TIWTDVDGVY SADPRKVNEA VILQTLSYQE AWEMSYFGAN VLHPRTIIPV 370 380 390 400 410 420 MRYNIPIVIR NIFNLSAPGT IICQPPEDDY DLKLTTPVKG FATIDNLALI NVEGTGMAGV 430 440 450 460 470 480 PGTASDIFGC VKDVGANVIM ISQASSEHSV CFAVPEKEVN AVSEALRSRF SEALQAGRLS 490 500 510 520 530 540 QIEVIPNCSI LAAVGQKMAS TPGVSCTLFS ALAKANINVR AISQGCSEYN VTVVIKREDS 550 560 570 580 590 600 VKALRAVHSR FFLSRTTLAM GIVGPGLIGA TLLDQLRDQA AVLKQEFNID LRVLGITGSK 610 620 630 640 650 660 KMLLSDIGID LSRWRELLNE KGTEADLDKF TQQVHGNHFI PNSVVVDCTA DSAIASRYYD 670 680 690 700 710 720 WLRKGIHVIT PNKKANSGPL DQYLKLRDLQ RKSYTHYFYE ATVGAGLPII STLRGLLETG 730 740 750 760 770 780 DKILRIEGIC SGTLSYLFNN FVGDRSFSEV VTEAKNAGFT EPDPRDDLSG TDVARKVIIL 790 800 810 820 830 840 ARESGLKLDL ADLPIRSLVP EPLKGCTSVE EFMEKLPQYD GDLAKERLDA ENSGEVLRYV 850 860 870 880 890 900 GVVDAVNQKG TVELRRYKKE HPFAQLAGSD NIIAFTTTRY KDHPLIVRGP GAGAQVTAGG 910 IFSDILRLAS YLGAPS
	Isoform 2 [UniParc]. Checksum: 1785CFCBF23709C7		859	94,426
	10 20 30 40 50 60 MATLKPSFTV SPPNSNPIRF GSFPPQCFLR VPKPRRLILP RFRKTTGGGG GLIRCELPDF 70 80 90 100 110 120 HLSATATTVS GVSTVNLVDQ VQIPKGEMWS VHKFGGTCVG NSQRIRNVAE VIINDNSERK 130 140 150 160 170 180 LVVVSAMSKV TDMMYDLIRK AQSRDDSYLS ALEAVLEKHR LTARDLLDGD DLASFLSHLH 190 200 210 220 230 240 NDISNLKAML RAIYIAGHAS ESFSDFVAGH GELWSAQMLS YVVRKTGLEC KWMDTRDVLI 250 260 270 280 290 300 VNPTSSNQVD PDFGESEKRL DKWFSLNPSK IIIATGFIAS TPQNIPTTLK RDGSDFSAAI 310 320 330 340 350 360 MGALLRARQV TIWTDVDGVY SADPRKVNEA VILQTLSYQE AWEMSYFGAN VLHPRTIIPV 370 380 390 400 410 420 MRYNIPIVIR NIFNLSAPGT IICQPPEDDY DLKLTTPVKG FATIDNLALI NVEGTGMAGV 430 440 450 460 470 480 PGTASDIFGC VKDVGANVIM ISQASSEHSV CFAVPEKEVN AVSEALRSRF SEALQAGRLS 490 500 510 520 530 540 QIEVIPNCSI LAAVGQKMAS TPGVSCTLFS ALAKANINVR AISQGCSEYN VTVVIKREDS 550 560 570 580 590 600 VKALRAVHSR FFLSRTTLAM GIVGPGLIGA TLLDQLRDQA AVLKQEFNID LRVLGITGSK 610 620 630 640 650 660 KMLLSDIGID LSRWRELLNE KGTEADLDKF TQQVHGNHFI PNSVVVDCTA DSAIASRYYD 670 680 690 700 710 720 WLRKGIHVIT PNKKANSGPL DQYLKLRDLQ RKSYTHYFYE ATVGAGLPII STLRGLLETG 730 740 750 760 770 780 DKILRIEGIC SGTLSYLFNN FVGDRSFSEV VTEAKNAGFT EPDPRDDLSG TDVARKVIIL 790 800 810 820 830 840 ARESGLKLDL ADLPIRSLVP EPLKGCTSVE EFMEKLPQYD GDLAKERLDA ENSGEVRLFT 850 TNVFPFDQCD HILTIYICM

References

	« Hide 'large scale' referencesShow 'large scale' references »
[1]	"Sequence and analysis of chromosome 4 of the plant Arabidopsis thaliana." Mayer K.F.X., Schueller C., Wambutt R., Murphy G., Volckaert G., Pohl T., Duesterhoeft A., Stiekema W., Entian K.-D., Terryn N., Harris B., Ansorge W., Brandt P., Grivell L.A., Rieger M., Weichselgartner M., de Simone V., Obermaier B. , Mache R., Mueller M., Kreis M., Delseny M., Puigdomenech P., Watson M., Schmidtheini T., Reichert B., Portetelle D., Perez-Alonso M., Boutry M., Bancroft I., Vos P., Hoheisel J., Zimmermann W., Wedler H., Ridley P., Langham S.-A., McCullagh B., Bilham L., Robben J., van der Schueren J., Grymonprez B., Chuang Y.-J., Vandenbussche F., Braeken M., Weltjens I., Voet M., Bastiaens I., Aert R., Defoor E., Weitzenegger T., Bothe G., Ramsperger U., Hilbert H., Braun M., Holzer E., Brandt A., Peters S., van Staveren M., Dirkse W., Mooijman P., Klein Lankhorst R., Rose M., Hauf J., Koetter P., Berneiser S., Hempel S., Feldpausch M., Lamberth S., Van den Daele H., De Keyser A., Buysshaert C., Gielen J., Villarroel R., De Clercq R., van Montagu M., Rogers J., Cronin A., Quail M.A., Bray-Allen S., Clark L., Doggett J., Hall S., Kay M., Lennard N., McLay K., Mayes R., Pettett A., Rajandream M.A., Lyne M., Benes V., Rechmann S., Borkova D., Bloecker H., Scharfe M., Grimm M., Loehnert T.-H., Dose S., de Haan M., Maarse A.C., Schaefer M., Mueller-Auer S., Gabel C., Fuchs M., Fartmann B., Granderath K., Dauner D., Herzl A., Neumann S., Argiriou A., Vitale D., Liguori R., Piravandi E., Massenet O., Quigley F., Clabauld G., Muendlein A., Felber R., Schnabl S., Hiller R., Schmidt W., Lecharny A., Aubourg S., Chefdor F., Cooke R., Berger C., Monfort A., Casacuberta E., Gibbons T., Weber N., Vandenbol M., Bargues M., Terol J., Torres A., Perez-Perez A., Purnelle B., Bent E., Johnson S., Tacon D., Jesse T., Heijnen L., Schwarz S., Scholler P., Heber S., Francs P., Bielke C., Frishman D., Haase D., Lemcke K., Mewes H.-W., Stocker S., Zaccaria P., Bevan M., Wilson R.K., de la Bastide M., Habermann K., Parnell L., Dedhia N., Gnoj L., Schutz K., Huang E., Spiegel L., Sekhon M., Murray J., Sheet P., Cordes M., Abu-Threideh J., Stoneking T., Kalicki J., Graves T., Harmon G., Edwards J., Latreille P., Courtney L., Cloud J., Abbott A., Scott K., Johnson D., Minx P., Bentley D., Fulton B., Miller N., Greco T., Kemp K., Kramer J., Fulton L., Mardis E., Dante M., Pepin K., Hillier L.W., Nelson J., Spieth J., Ryan E., Andrews S., Geisel C., Layman D., Du H., Ali J., Berghoff A., Jones K., Drone K., Cotton M., Joshu C., Antonoiu B., Zidanic M., Strong C., Sun H., Lamar B., Yordan C., Ma P., Zhong J., Preston R., Vil D., Shekher M., Matero A., Shah R., Swaby I.K., O'Shaughnessy A., Rodriguez M., Hoffman J., Till S., Granat S., Shohdy N., Hasegawa A., Hameed A., Lodhi M., Johnson A., Chen E., Marra M.A., Martienssen R., McCombie W.R. Nature 402:769-777(1999) [PubMed: 10617198] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA]. Strain: cv. Columbia.
[2]	"Overproduction, purification, and characterization of recombinant bifunctional threonine-sensitive aspartate kinase-homoserine dehydrogenase from Arabidopsis thaliana." Paris S., Wessel P.M., Dumas R. Protein Expr. Purif. 24:105-110(2002) [PubMed: 11812230] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [MRNA] (ISOFORM 1), BIOPHYSICOCHEMICAL PROPERTIES.
[3]	"Whole genome sequence comparisons and 'full-length' cDNA sequences: a combined approach to evaluate and improve Arabidopsis genome annotation." Castelli V., Aury J.-M., Jaillon O., Wincker P., Clepet C., Menard M., Cruaud C., Quetier F., Scarpelli C., Schaechter V., Temple G., Caboche M., Weissenbach J., Salanoubat M. Genome Res. 14:406-413(2004) [PubMed: 14993207] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE MRNA] (ISOFORM 1). Strain: cv. Columbia.
[4]	"Mechanism of control of Arabidopsis thaliana aspartate kinase-homoserine dehydrogenase by threonine." Paris S., Viemon C., Curien G., Dumas R. J. Biol. Chem. 278:5361-5366(2003) [PubMed: 12435751] [Abstract] Cited for: ENZYME REGULATION, MUTAGENESIS OF ILE-441; GLN-443; ILE-522 AND GLN-524.
[5]	"Identification of six novel allosteric effectors of Arabidopsis thaliana aspartate kinase-homoserine dehydrogenase isoforms. Physiological context sets the specificity." Curien G., Ravanel S., Robert M., Dumas R. J. Biol. Chem. 280:41178-41183(2005) [PubMed: 16216875] [Abstract] Cited for: ENZYME REGULATION, BIOPHYSICOCHEMICAL PROPERTIES.

Cross-references

Sequence databases
EMBLGenBankDDBJ	AL024486 Genomic DNA. Translation: CAA19688.1. AL161551 Genomic DNA. Translation: CAB78973.1. BX827863 mRNA. No translation available.
PIR	T04752.
RefSeq	NP_193706.2. NP_974576.1.
UniGene	At.32787
3D structure databases
HSSP	HSSP built from PDB template 1EBF based on UniProtKB P31116.
ModBase	Search...
Genome annotation databases
GeneID	827715.
GenomeReviews	Gene locus AT4G19710 in contig CT486007_GR.
Organism-specific databases
TAIR	At4g19710.
Gene expression databases
ArrayExpress	O81852.
GermOnline	AT4G19710. Arabidopsis thaliana.
Family and domain databases
InterPro	IPR002912. ACT_bd. IPR001048. Asp/Glu/Uridylate_kinase. IPR005106. Asp/hSer_DHase_NAD-bd. IPR001341. Asp_kin_reg. IPR011147. bifunc_aspartokin/hSer_DHase. IPR001342. hSer_DHase_cat. IPR016040. NAD(P)-bd. [Graphical view]
Gene3D	G3DSA:3.40.1160.10. Aa_kinase. 1 hit. G3DSA:3.40.50.720. NAD(P)-bd. 1 hit.
Pfam	PF00696. AA_kinase. 1 hit. PF01842. ACT. 2 hits. PF00742. Homoserine_dh. 1 hit. PF03447. NAD_binding_3. 1 hit. [Graphical view]
PIRSF	PIRSF000727. ThrA. 1 hit.
TIGRFAMs	TIGR00657. asp_kinases. 1 hit.
PROSITE	PS00324. ASPARTOKINASE. 1 hit. PS01042. HOMOSER_DHGENASE. 1 hit. [Graphical view]
ProDom	O81852. [Graphical view] [Entries sharing at least one domain]
BLOCKS	Search...
Other Resources
ProtoNet	Search...

Entry information

Entry name

AKH2_ARATH

Accession

Primary (citable) accession number: O81852
Secondary accession number(s): Q3E9Y8

Entry history

Integrated into UniProtKB/Swiss-Prot:	July 11, 2006
Last sequence update:	November 1, 1998
Last modified:	July 22, 2008
This is version 56 of the entry and version 1 of the sequence. [Complete history]

Entry status

Reviewed (UniProtKB/Swiss-Prot)

Annotation project

PPAP (Plant Proteome Annotation Project)