ID   RBS_XANFL               Reviewed;         133 AA.
AC   P23012;
DT   01-NOV-1991, integrated into UniProtKB/Swiss-Prot.
DT   01-NOV-1991, sequence version 1.
DT   25-MAY-2022, entry version 83.
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=cfxS;
OS   Xanthobacter flavus.
OC   Bacteria; Proteobacteria; Alphaproteobacteria; Hyphomicrobiales;
OC   Xanthobacteraceae; Xanthobacter.
OX   NCBI_TaxID=281;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RC   STRAIN=H4-14;
RX   PubMed=1900916; DOI=10.1007/bf00269865;
RA   Meijer W.G., Arnberg A.C., Enequist H.G., Terpstra P., Lidstrom M.E.,
RA   Dijkhuizen L.;
RT   "Identification and organization of carbon dioxide fixation genes in
RT   Xanthobacter flavus H4-14.";
RL   Mol. Gen. Genet. 225:320-330(1991).
RN   [2]
RP   FUNCTION, CATALYTIC ACTIVITY, AND BIOPHYSICOCHEMICAL PROPERTIES.
RC   STRAIN=H4-14;
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=23 uM for ribulose 1,5-bisphosphate {ECO:0000269|PubMed:9882445};
CC         KM=100 uM for CO(2) {ECO:0000269|PubMed:9882445};
CC         Vmax=1.8 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 44.;
CC   -!- SUBUNIT: Heterohexadecamer of 8 large and 8 small subunits.
CC       {ECO:0000255|HAMAP-Rule:MF_00859, ECO:0000305|PubMed:9882445}.
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; X17252; CAA35116.1; -; Genomic_DNA.
DR   PIR; S13574; RKQXSX.
DR   AlphaFoldDB; P23012; -.
DR   SMR; P23012; -.
DR   SABIO-RK; P23012; -.
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   Calvin cycle; Carbon dioxide fixation.
FT   CHAIN           1..133
FT                   /note="Ribulose bisphosphate carboxylase small subunit"
FT                   /id="PRO_0000198632"
SQ   SEQUENCE   133 AA;  15318 MW;  C21BC18DBD95B3B4 CRC64;
     MRITQGTFSF LPDLTAAQVK AQIQYALDQN WAVSVEYTDD PHPRNTYWEM WGLPMFDLRD
     AAGVYGEVEA CRTAHPGKYV RVNAFDSNRG WETVRLSFIV QRPEKEDGFR LDRTEGPGRT
     QRYALQHRSY AAG