ID A0A926YGU5_9CYAN Unreviewed; 104 AA.
AC A0A926YGU5;
DT 22-FEB-2023, integrated into UniProtKB/TrEMBL.
DT 22-FEB-2023, sequence version 1.
DT 18-JUN-2025, entry version 11.
DE RecName: Full=Circadian clock oscillator protein KaiB {ECO:0000256|HAMAP-Rule:MF_01835};
GN Name=kaiB {ECO:0000256|HAMAP-Rule:MF_01835,
GN ECO:0000313|EMBL:MBD2020465.1};
GN ORFNames=H6F43_09720 {ECO:0000313|EMBL:MBD2020465.1};
OS Leptolyngbya sp. FACHB-36.
OC Bacteria; Bacillati; Cyanobacteriota; Cyanophyceae; Leptolyngbyales;
OC Leptolyngbyaceae; Leptolyngbya group; Leptolyngbya.
OX NCBI_TaxID=2692808 {ECO:0000313|EMBL:MBD2020465.1, ECO:0000313|Proteomes:UP000661179};
RN [1] {ECO:0000313|EMBL:MBD2020465.1}
RP NUCLEOTIDE SEQUENCE.
RC STRAIN=FACHB-36 {ECO:0000313|EMBL:MBD2020465.1};
RX PubMed=32943748;
RA Chen M.Y., Teng W.K., Zhao L., Hu C.X., Zhou Y.K., Han B.P., Song L.R.,
RA Shu W.S.;
RT "Comparative genomics reveals insights into cyanobacterial evolution and
RT habitat adaptation.";
RL ISME J. 0:0-0(2020).
RN [2] {ECO:0000313|EMBL:MBD2020465.1}
RP NUCLEOTIDE SEQUENCE.
RC STRAIN=FACHB-36 {ECO:0000313|EMBL:MBD2020465.1};
RA Chen M., Teng W., Zhao L., Hu C., Zhou Y., Han B., Song L., Shu W.;
RL Submitted (AUG-2020) to the EMBL/GenBank/DDBJ databases.
CC -!- FUNCTION: A metamorphic protein which reversibly switches between an
CC inactive tetrameric fold and a rare, thioredoxin-like monomeric fold
CC (KaiB(fs)). KaiB(fs) binds phospho-KaiC, KaiA and CikA. KaiA and CikA
CC compete for binding to KaiB(fs), and KaiB(fs) and SasA compete for
CC binding to KaiC, thus the clock oscillator and output signal pathway
CC are tightly coupled. {ECO:0000256|HAMAP-Rule:MF_01835}.
CC -!- FUNCTION: Key component of the KaiABC oscillator complex, which
CC constitutes the main circadian regulator in cyanobacteria. Complex
CC composition changes during the circadian cycle to control KaiC
CC phosphorylation. KaiA stimulates KaiC autophosphorylation, while KaiB
CC sequesters KaiA, leading to KaiC autodephosphorylation. Phospho-Ser-431
CC KaiC accumulation triggers binding of KaiB to form the KaiB(6):KaiC(6)
CC complex, leading to changes in output regulators CikA and SasA. KaiB
CC switches to a thioredoxin-like fold (KaiB(fs)) when bound to KaiC.
CC KaiB(6):KaiC(6) formation exposes a site for KaiA binding that
CC sequesters KaiA from KaiC, making the KaiC(6):KaiB(6):KaiA(12) complex
CC that results in KaiC autodephosphorylation. {ECO:0000256|HAMAP-
CC Rule:MF_01835}.
CC -!- SUBUNIT: The KaiABC complex composition changes during the circadian
CC cycle to control KaiC phosphorylation. Complexes KaiC(6), KaiA(2-
CC 4):KaiC(6), KaiB(6):KaiC(6) and KaiC(6):KaiB(6):KaiA(12) are among the
CC most important forms, many form cooperatively. Undergoes a major
CC conformational rearrangment; in the free state forms homotetramers as a
CC dimer of dimers. When bound to the CI domain of KaiC switches to a
CC monomeric thioredoxin-fold (KaiB(fs)). KaiB(fs) binds CikA, leading it
CC to dephosphorylate phospho-RpaA. {ECO:0000256|HAMAP-Rule:MF_01835}.
CC -!- DOMAIN: Has 2 forms, fold switches to a thioredoxin-like fold
CC (KaiB(fs)) when bound to KaiC. {ECO:0000256|HAMAP-Rule:MF_01835}.
CC -!- SIMILARITY: Belongs to the KaiB family. {ECO:0000256|ARBA:ARBA00061074,
CC ECO:0000256|HAMAP-Rule:MF_01835}.
CC -!- CAUTION: The sequence shown here is derived from an EMBL/GenBank/DDBJ
CC whole genome shotgun (WGS) entry which is preliminary data.
CC {ECO:0000313|EMBL:MBD2020465.1}.
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DR EMBL; JACJPG010000339; MBD2020465.1; -; Genomic_DNA.
DR RefSeq; WP_190342583.1; NZ_JACJPG010000339.1.
DR Proteomes; UP000661179; Unassembled WGS sequence.
DR GO; GO:0007623; P:circadian rhythm; IEA:UniProtKB-UniRule.
DR CDD; cd02978; KaiB_like; 1.
DR FunFam; 3.40.30.10:FF:000180; Circadian clock protein KaiB; 1.
DR Gene3D; 3.40.30.10; Glutaredoxin; 1.
DR HAMAP; MF_01835; KaiB; 1.
DR InterPro; IPR013474; Circ_KaiB.
DR InterPro; IPR039022; KaiB-like.
DR InterPro; IPR011649; KaiB_domain.
DR InterPro; IPR036249; Thioredoxin-like_sf.
DR NCBIfam; TIGR02654; circ_KaiB; 1.
DR NCBIfam; NF006798; PRK09301.1; 1.
DR PANTHER; PTHR41709:SF2; CIRCADIAN CLOCK PROTEIN KAIB2; 1.
DR PANTHER; PTHR41709; KAIB-LIKE PROTEIN 1; 1.
DR Pfam; PF07689; KaiB; 1.
DR SMART; SM01248; KaiB; 1.
DR SUPFAM; SSF52833; Thioredoxin-like; 1.
PE 3: Inferred from homology;
KW Biological rhythms {ECO:0000256|ARBA:ARBA00023108, ECO:0000256|HAMAP-
KW Rule:MF_01835}; Reference proteome {ECO:0000313|Proteomes:UP000661179}.
FT DOMAIN 11..92
FT /note="KaiB"
FT /evidence="ECO:0000259|SMART:SM01248"
SQ SEQUENCE 104 AA; 11640 MW; 3B0A4D615A30AFC8 CRC64;
MSPSKKTYVL KLYVAGNTPN SIRALKTLNN ILETEFQGVY ALKVIDVMKS PQLAEEDKIL
ATPTLAKILP PPVRKIIGDL SDREKVLIGL DLLYEELRDD DSEL
//