ID   RBS_PICP2               Reviewed;         111 AA.
AC   Q44178; B1XPS0;
DT   15-DEC-1998, integrated into UniProtKB/Swiss-Prot.
DT   01-NOV-1996, sequence version 1.
DT   27-MAR-2024, entry version 126.
DE   RecName: Full=Ribulose bisphosphate carboxylase small subunit {ECO:0000255|HAMAP-Rule:MF_00859};
DE            Short=RuBisCO small subunit {ECO:0000255|HAMAP-Rule:MF_00859};
GN   Name=cbbS {ECO:0000255|HAMAP-Rule:MF_00859};
GN   Synonyms=rbcS {ECO:0000255|HAMAP-Rule:MF_00859};
GN   OrderedLocusNames=SYNPCC7002_A1796;
OS   Picosynechococcus sp. (strain ATCC 27264 / PCC 7002 / PR-6) (Agmenellum
OS   quadruplicatum).
OC   Bacteria; Cyanobacteriota; Cyanophyceae; Oscillatoriophycideae;
OC   Chroococcales; Geminocystaceae; Picosynechococcus.
OX   NCBI_TaxID=32049;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RA   Akiyama H., Kanai S., Hirano M., Sugimoto M., Kiyohara M.;
RL   Submitted (JUN-1994) to the EMBL/GenBank/DDBJ databases.
RN   [2]
RP   NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
RC   STRAIN=ATCC 27264 / PCC 7002 / PR-6;
RA   Li T., Zhao J., Zhao C., Liu Z., Zhao F., Marquardt J., Nomura C.T.,
RA   Persson S., Detter J.C., Richardson P.M., Lanz C., Schuster S.C., Wang J.,
RA   Li S., Huang X., Cai T., Yu Z., Luo J., Zhao J., Bryant D.A.;
RT   "Complete sequence of Synechococcus sp. PCC 7002.";
RL   Submitted (FEB-2008) to the EMBL/GenBank/DDBJ databases.
RN   [3]
RP   SUBUNIT.
RC   STRAIN=ATCC 27264 / PCC 7002 / PR-6;
RX   PubMed=17574029; DOI=10.1016/j.cell.2007.04.025;
RA   Saschenbrecker S., Bracher A., Rao K.V., Rao B.V., Hartl F.U.,
RA   Hayer-Hartl M.;
RT   "Structure and function of RbcX, an assembly chaperone for hexadecameric
RT   Rubisco.";
RL   Cell 129:1189-1200(2007).
RN   [4]
RP   RUBISCO FOLDING AND ASSEMBLY.
RC   STRAIN=ATCC 27264 / PCC 7002 / PR-6;
RX   PubMed=26237510; DOI=10.1038/nsmb.3062;
RA   Hauser T., Bhat J.Y., Milicic G., Wendler P., Hartl F.U., Bracher A.,
RA   Hayer-Hartl M.;
RT   "Structure and mechanism of the Rubisco-assembly chaperone Raf1.";
RL   Nat. Struct. Mol. Biol. 22:720-728(2015).
CC   -!- FUNCTION: RuBisCO catalyzes two reactions: the carboxylation of D-
CC       ribulose 1,5-bisphosphate, the primary event in carbon dioxide
CC       fixation, as well as the oxidative fragmentation of the pentose
CC       substrate in the photorespiration process. Both reactions occur
CC       simultaneously and in competition at the same active site. Although the
CC       small subunit is not catalytic it is essential for maximal activity.
CC       {ECO:0000255|HAMAP-Rule:MF_00859}.
CC   -!- SUBUNIT: Heterohexadecamer of 8 large and 8 small subunits.
CC       {ECO:0000255|HAMAP-Rule:MF_00859, ECO:0000305|PubMed:17574029}.
CC   -!- SUBCELLULAR LOCATION: Carboxysome {ECO:0000255|HAMAP-Rule:MF_00859}.
CC   -!- MISCELLANEOUS: RuBisCO folding and assembly commences when the nascent
CC       large subunit folds with the help of the chaperonin GroEL-GroES.
CC       Requires homodimeric RuBisCO chaperone RbcX2 to assemble into RbcL8
CC       octamers, making RbcL8-(RbcX2)8. The exposed C-terminus of RbcL binds
CC       in a cleft in RbcX2 (PubMed:17574029). RbcX2 is displaced by RbcS; as
CC       RbcX2 is removed RbcS mediates the ordering of an internal RbcL loop
CC       (Thr-63-Leu-69) in a catalytically active conformation (By similarity).
CC       Interacts with accumulation factor Raf1; dimeric Raf1 acts after
CC       chaperonin GroEL-GroES, binding to RbcL(2) leading to an RbcL8-Raf1(8)
CC       complex. RbcS displaces Raf1, resulting in holoenzyme formation
CC       (Probable). {ECO:0000250|UniProtKB:P00880, ECO:0000269|PubMed:17574029,
CC       ECO:0000305|PubMed:26237510}.
CC   -!- MISCELLANEOUS: The basic functional RuBisCO is composed of a large
CC       chain homodimer in a 'head-to-tail' conformation. In form I RuBisCO
CC       this homodimer is arranged in a barrel-like tetramer with the small
CC       subunits forming a tetrameric 'cap' on each end of the 'barrel'.
CC       {ECO:0000255|HAMAP-Rule:MF_00859}.
CC   -!- SIMILARITY: Belongs to the RuBisCO small chain family.
CC       {ECO:0000255|HAMAP-Rule:MF_00859}.
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DR   EMBL; D13971; BAA03078.1; -; Genomic_DNA.
DR   EMBL; CP000951; ACA99784.1; -; Genomic_DNA.
DR   RefSeq; WP_012307407.1; NZ_JAHHPU010000002.1.
DR   AlphaFoldDB; Q44178; -.
DR   SMR; Q44178; -.
DR   STRING; 32049.SYNPCC7002_A1796; -.
DR   KEGG; syp:SYNPCC7002_A1796; -.
DR   eggNOG; COG4451; Bacteria.
DR   HOGENOM; CLU_098114_2_0_3; -.
DR   Proteomes; UP000001688; Chromosome.
DR   GO; GO:0031470; C:carboxysome; IEA:UniProtKB-SubCell.
DR   GO; GO:0016984; F:ribulose-bisphosphate carboxylase activity; IDA:CACAO.
DR   GO; GO:0009853; P:photorespiration; IEA:UniProtKB-KW.
DR   GO; GO:0019253; P:reductive pentose-phosphate cycle; IEA:UniProtKB-UniRule.
DR   CDD; cd03527; RuBisCO_small; 1.
DR   Gene3D; 3.30.190.10; Ribulose bisphosphate carboxylase, small subunit; 1.
DR   HAMAP; MF_00859; RuBisCO_S_bact; 1.
DR   InterPro; IPR024681; RuBisCO_ssu.
DR   InterPro; IPR000894; RuBisCO_ssu_dom.
DR   InterPro; IPR036385; RuBisCO_ssu_sf.
DR   PANTHER; PTHR31262; RIBULOSE BISPHOSPHATE CARBOXYLASE SMALL CHAIN 1, CHLOROPLASTIC; 1.
DR   Pfam; PF00101; RuBisCO_small; 1.
DR   PRINTS; PR00152; RUBISCOSMALL.
DR   SMART; SM00961; RuBisCO_small; 1.
DR   SUPFAM; SSF55239; RuBisCO, small subunit; 1.
PE   1: Evidence at protein level;
KW   Bacterial microcompartment; Calvin cycle; Carbon dioxide fixation;
KW   Carboxysome; Photorespiration; Photosynthesis; Reference proteome.
FT   CHAIN           1..111
FT                   /note="Ribulose bisphosphate carboxylase small subunit"
FT                   /id="PRO_0000198623"
SQ   SEQUENCE   111 AA;  13212 MW;  182FA0950AC8EF96 CRC64;
     MKTLPKEKRY ETLSYLPPLS DQQIARQVQY MMDQGYIPGI EFEKDPTPEL HHWTLWKLPL
     FNASSAQEVL NEVRECRSEY SDCYIRVVGF DNIKQCQTVS FIVYKPNQTR Y
//