ID   RBS_CERSP               Reviewed;         129 AA.
AC   P27998;
DT   01-AUG-1992, integrated into UniProtKB/Swiss-Prot.
DT   01-AUG-1992, sequence version 1.
DT   25-MAY-2022, entry version 86.
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}; Synonyms=rbcS;
OS   Cereibacter sphaeroides (Rhodobacter sphaeroides).
OC   Bacteria; Proteobacteria; Alphaproteobacteria; Rhodobacterales;
OC   Rhodobacteraceae; Cereibacter.
OX   NCBI_TaxID=1063;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA], AND INDUCTION.
RX   PubMed=1907281; DOI=10.1016/s0021-9258(18)98734-x;
RA   Gibson J.L., Falcone D.L., Tabita F.R.;
RT   "Nucleotide sequence, transcriptional analysis, and expression of genes
RT   encoded within the form I CO2 fixation operon of Rhodobacter sphaeroides.";
RL   J. Biol. Chem. 266:14646-14653(1991).
RN   [2]
RP   FUNCTION, CATALYTIC ACTIVITY, AND BIOPHYSICOCHEMICAL PROPERTIES.
RC   STRAIN=FI;
RX   PubMed=9882445; DOI=10.1006/abbi.1998.0979;
RA   Horken K.M., Tabita F.R.;
RT   "Closely related form I ribulose bisphosphate carboxylase/oxygenase
RT   molecules that possess different CO2/O2 substrate specificities.";
RL   Arch. Biochem. Biophys. 361:183-194(1999).
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. Both reactions occur simultaneously and in competition at
CC       the same active site. Although the small subunit is not catalytic it is
CC       essential for maximal activity. {ECO:0000255|HAMAP-Rule:MF_00859,
CC       ECO:0000269|PubMed:9882445}.
CC   -!- BIOPHYSICOCHEMICAL PROPERTIES:
CC       Kinetic parameters:
CC         KM=50 uM for ribulose 1,5-bisphosphate {ECO:0000269|PubMed:9882445};
CC         KM=22 uM for CO(2) {ECO:0000269|PubMed:9882445};
CC         Vmax=2.5 umol/min/mg enzyme with CO(2) as substrate
CC         {ECO:0000269|PubMed:9882445};
CC         Note=The CO(2)/O(2) specificity factor (tau) is 56.;
CC   -!- SUBUNIT: Heterohexadecamer of 8 large and 8 small subunits.
CC       {ECO:0000255|HAMAP-Rule:MF_00859, ECO:0000305|PubMed:9882445}.
CC   -!- INDUCTION: Expression of this form I ribulose-bisphosphate carboxylase
CC       operon predominates when carbon dioxide is limiting.
CC       {ECO:0000269|PubMed:1907281}.
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}.
CC   ---------------------------------------------------------------------------
CC   Copyrighted by the UniProt Consortium, see https://www.uniprot.org/terms
CC   Distributed under the Creative Commons Attribution (CC BY 4.0) License
CC   ---------------------------------------------------------------------------
DR   EMBL; M64624; AAA26116.1; -; Genomic_DNA.
DR   PIR; E40767; RKRFAS.
DR   PDB; 5NV3; EM; 3.39 A; I/J/K/L/M/N/O/P=1-129.
DR   PDBsum; 5NV3; -.
DR   AlphaFoldDB; P27998; -.
DR   SMR; P27998; -.
DR   SABIO-RK; P27998; -.
DR   GO; GO:0019253; P:reductive pentose-phosphate cycle; IEA:UniProtKB-KW.
DR   CDD; cd03527; RuBisCO_small; 1.
DR   Gene3D; 3.30.190.10; -; 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; PTHR31262; 1.
DR   Pfam; PF00101; RuBisCO_small; 1.
DR   SMART; SM00961; RuBisCO_small; 1.
DR   SUPFAM; SSF55239; SSF55239; 1.
PE   1: Evidence at protein level;
KW   3D-structure; Calvin cycle; Carbon dioxide fixation; Photosynthesis.
FT   CHAIN           1..129
FT                   /note="Ribulose bisphosphate carboxylase small subunit"
FT                   /id="PRO_0000198622"
FT   HELIX           16..29
FT                   /evidence="ECO:0007829|PDB:5NV3"
FT   STRAND          32..39
FT                   /evidence="ECO:0007829|PDB:5NV3"
FT   HELIX           61..74
FT                   /evidence="ECO:0007829|PDB:5NV3"
FT   STRAND          76..85
FT                   /evidence="ECO:0007829|PDB:5NV3"
FT   STRAND          88..90
FT                   /evidence="ECO:0007829|PDB:5NV3"
FT   STRAND          93..101
FT                   /evidence="ECO:0007829|PDB:5NV3"
FT   STRAND          109..115
FT                   /evidence="ECO:0007829|PDB:5NV3"
FT   STRAND          121..127
FT                   /evidence="ECO:0007829|PDB:5NV3"
SQ   SEQUENCE   129 AA;  15164 MW;  7BDEFED2F5C8D74E CRC64;
     MRITQGCFSF LPDLTDEQIS AQVDYCLGRG WAVSLEHTDD PHPRNTYWEM WGMPMFDLRD
     PKGVMIELDE CRKAWPGRYI RINAFDSTRG FETVTMSFIV NRPEVEPSLR MERTEVDGRS
     IRYTHSIVR