ID   PSBU_PHOLA              Reviewed;         143 AA.
AC   P20094;
DT   01-FEB-1991, integrated into UniProtKB/Swiss-Prot.
DT   01-FEB-1991, sequence version 1.
DT   25-MAY-2022, entry version 77.
DE   RecName: Full=Photosystem II 12 kDa extrinsic protein {ECO:0000255|HAMAP-Rule:MF_00589};
DE   AltName: Full=9 kDa polypeptide;
DE   AltName: Full=PS II complex 12 kDa extrinsic protein {ECO:0000255|HAMAP-Rule:MF_00589};
DE   AltName: Full=PSII-U {ECO:0000255|HAMAP-Rule:MF_00589};
DE   Flags: Precursor;
GN   Name=psbU {ECO:0000255|HAMAP-Rule:MF_00589};
OS   Phormidium laminosum.
OC   Bacteria; Cyanobacteria; Oscillatoriophycideae; Oscillatoriales;
OC   Oscillatoriaceae; Phormidium.
OX   NCBI_TaxID=32059;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA], AND PARTIAL PROTEIN SEQUENCE.
RC   STRAIN=OH-1-P-CL1;
RX   PubMed=2501648; DOI=10.1007/bf00334373;
RA   Wallace T.P., Stewart A.C., Pappin D., Howe C.J.;
RT   "Gene sequence for the 9 kDa component of Photosystem II from the
RT   cyanobacterium Phormidium laminosum indicates similarities between
RT   cyanobacterial and other leader sequences.";
RL   Mol. Gen. Genet. 216:334-339(1989).
CC   -!- FUNCTION: Stabilizes the structure of photosystem II oxygen-evolving
CC       complex (OEC), the ion environment of oxygen evolution and protects the
CC       OEC against heat-induced inactivation. {ECO:0000255|HAMAP-
CC       Rule:MF_00589}.
CC   -!- SUBUNIT: With PsbO,P,Q and V forms the oxygen-evolving complex of
CC       photosystem II. {ECO:0000255|HAMAP-Rule:MF_00589}.
CC   -!- SUBCELLULAR LOCATION: Cellular thylakoid membrane; Peripheral membrane
CC       protein; Lumenal side. Note=Associated with photosystem II at the
CC       lumenal side of the thylakoid membrane. {ECO:0000250}.
CC   -!- SIMILARITY: Belongs to the PsbU family. {ECO:0000255|HAMAP-
CC       Rule:MF_00589}.
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DR   EMBL; X52660; CAA36886.1; -; Genomic_DNA.
DR   PIR; S04413; S04413.
DR   AlphaFoldDB; P20094; -.
DR   SMR; P20094; -.
DR   GO; GO:0019898; C:extrinsic component of membrane; IEA:InterPro.
DR   GO; GO:0009654; C:photosystem II oxygen evolving complex; IEA:InterPro.
DR   GO; GO:0031676; C:plasma membrane-derived thylakoid membrane; IEA:UniProtKB-SubCell.
DR   GO; GO:0015979; P:photosynthesis; IEA:UniProtKB-UniRule.
DR   GO; GO:0042549; P:photosystem II stabilization; IEA:InterPro.
DR   HAMAP; MF_00589; PSII_PsbU; 1.
DR   InterPro; IPR010527; PSII_PsbU.
DR   Pfam; PF06514; PsbU; 1.
PE   1: Evidence at protein level;
KW   Direct protein sequencing; Electron transport; Membrane; Photosynthesis;
KW   Photosystem II; Signal; Thylakoid; Transport.
FT   SIGNAL          1..29
FT                   /evidence="ECO:0000255|HAMAP-Rule:MF_00589"
FT   PROPEP          30..44
FT                   /id="PRO_0000029599"
FT   CHAIN           45..143
FT                   /note="Photosystem II 12 kDa extrinsic protein"
FT                   /id="PRO_0000029600"
SQ   SEQUENCE   143 AA;  15810 MW;  2EAA30E460B73C55 CRC64;
     MKRLVGVLMI LGLMLTSWGL LGSPQTAIAA SLSPLSFNPS PVLAEQQFRN AMDDKLATDF
     GKKIDLNNTN VRAFMQYPGM YPTLARMILK NAPFESVEDV LKMPGLTDTQ KEILKNNFSN
     FVVSPPLDAL VEGGDRFNNG IYR