ID   RBS_PORAE               Reviewed;         138 AA.
AC   Q09125;
DT   01-FEB-1995, integrated into UniProtKB/Swiss-Prot.
DT   01-FEB-1995, sequence version 1.
DT   25-MAY-2022, entry version 90.
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=rbcS {ECO:0000255|HAMAP-Rule:MF_00859};
OS   Porphyridium aerugineum (Red microalga).
OG   Plastid; Chloroplast.
OC   Eukaryota; Rhodophyta; Bangiophyceae; Porphyridiales; Porphyridiaceae;
OC   Porphyridium.
OX   NCBI_TaxID=2792;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RX   PubMed=2598276; DOI=10.1007/bf00391478;
RA   Valentin K.-U., Zetsche K.;
RT   "The genes of both subunits of ribulose-1,5-bisphosphate carboxylase
RT   constitute an operon on the plastome of a red alga.";
RL   Curr. Genet. 16:203-209(1989).
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}.
CC   -!- SUBCELLULAR LOCATION: Plastid, chloroplast {ECO:0000255|HAMAP-
CC       Rule:MF_00859}.
CC   -!- MISCELLANEOUS: In this alga, in contrast to plants, the small subunit
CC       is encoded in the chloroplast.
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; X17597; -; NOT_ANNOTATED_CDS; Genomic_DNA.
DR   PIR; B48330; B48330.
DR   AlphaFoldDB; Q09125; -.
DR   SMR; Q09125; -.
DR   GO; GO:0009507; C:chloroplast; IEA:UniProtKB-SubCell.
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   3: Inferred from homology;
KW   Calvin cycle; Carbon dioxide fixation; Chloroplast; Photorespiration;
KW   Photosynthesis; Plastid.
FT   CHAIN           1..138
FT                   /note="Ribulose bisphosphate carboxylase small subunit"
FT                   /id="PRO_0000198603"
SQ   SEQUENCE   138 AA;  15959 MW;  92B354951912A74C CRC64;
     MRLTQGTFSF LPDLTDAQIQ KQVQYAVSKK WAVSVEYTDD PHPRNSFWEL WGLPLFDVKD
     ASALMYEIAA CRKAKPNYYI KVNAFDNTRG VESCCLSFII NRPINEPGFH LERQEVQGRN
     ILYTIKSYAV NKPEGSRY