AC MF_01836; DC Protein; auto TR HAMAP; MF_01836; -; 1; level=0 XX Names: KaiC XX ID KAIC DE RecName: Full=Circadian clock oscillator protein KaiC; DE EC=2.7.11.1; DE EC=3.6.4.-; GN Name=kaiC; XX case not CC -!- FUNCTION: Central 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. Clock output CC pathways impact the RpaA transcriptional regulator. KaiC enhances the CC autophosphorylation activity of SasA, which then transfers its CC phosphate group to RpaA to activate it. KaiB and KaiC together enhance CC the phospho-RpaA dephosphatase activity of CikA. CC -!- FUNCTION: Has a weak, temperature-independent ATPase activity; ATPase CC activity defines the circadian period. The phosphorylation state of CC KaiC modulates its ATPase activity and effects KaiB binding. CC -!- CATALYTIC ACTIVITY: CC Reaction=ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl- CC [protein]; Xref=Rhea:RHEA:17989, Rhea:RHEA-COMP:9863, Rhea:RHEA- CC COMP:11604, ChEBI:CHEBI:15378, ChEBI:CHEBI:29999, ChEBI:CHEBI:30616, CC ChEBI:CHEBI:83421, ChEBI:CHEBI:456216; EC=2.7.11.1; CC -!- CATALYTIC ACTIVITY: CC Reaction=ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L- CC threonyl-[protein]; Xref=Rhea:RHEA:46608, Rhea:RHEA-COMP:11060, CC Rhea:RHEA-COMP:11605, ChEBI:CHEBI:15378, ChEBI:CHEBI:30013, CC ChEBI:CHEBI:30616, ChEBI:CHEBI:61977, ChEBI:CHEBI:456216; CC EC=2.7.11.1; CC -!- CATALYTIC ACTIVITY: CC Reaction=ATP + H2O = ADP + H(+) + phosphate; Xref=Rhea:RHEA:13065, CC ChEBI:CHEBI:15377, ChEBI:CHEBI:15378, ChEBI:CHEBI:30616, CC ChEBI:CHEBI:43474, ChEBI:CHEBI:456216; CC -!- COFACTOR: CC Name=Mg(2+); Xref=ChEBI:CHEBI:18420; CC Note=Binds 2 Mg(2+) ions per subunit, one in each domain. Mg(2+) is CC required for hexamerization and phosphatase activity. CC -!- ACTIVITY REGULATION: The interaction with KaiA enhances its CC phosphorylation status, while the interaction with KaiB decreases it. CC -!- SUBUNIT: Homohexamer; hexamerization is dependent on ATP-binding. The CC KaiABC complex composition changes during the circadian cycle to CC control KaiC phosphorylation. Complexes KaiC(6), KaiA(2-4):KaiC(6), CC KaiB(6):KaiC(6) and KaiC(6):KaiB(6):KaiA(12) are among the most CC important forms, many form cooperatively. KaiC interacts with SasA, CC activating its autokinase function and leading to RpaA activation. CC -!- DOMAIN: In the homohexamer the 2 domains (called CI and CII) self- CC associate to each form a 'donut' layer; the compactness and local CC conformation of the domains varies over the cell cycle and impacts CC function. CII has the autokinase and autophosphatase activities, both CC CI and CII have (weak) ATPase activity; CI has the clock pacemaker CC role. CC -!- PTM: Phosphorylated on serine and threonine residues by autocatalysis. CC Has a 4 step phosphorylation cycle; the autokinase acts first on #{Thr- CC 432}, then #{Ser-431}. When #{Ser-431} is modified KaiC switches to an CC autophosphatase mode, acting first on phospho-#{Thr-432} then CC phospho-#{Ser-431}. end case case CC -!- FUNCTION: Central component of the KaiBC oscillator complex, which CC constitutes the main circadian regulator in cyanobacteria. Its CC composition changes during the circadian cycle to control KaiC CC phosphorylation. Autophosphorylates and has a weak ATPase activity; CC ATPase activity defines the circadian period. CC -!- CATALYTIC ACTIVITY: CC Reaction=ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl- CC [protein]; Xref=Rhea:RHEA:17989, Rhea:RHEA-COMP:9863, Rhea:RHEA- CC COMP:11604, ChEBI:CHEBI:15378, ChEBI:CHEBI:29999, ChEBI:CHEBI:30616, CC ChEBI:CHEBI:83421, ChEBI:CHEBI:456216; EC=2.7.11.1; CC -!- CATALYTIC ACTIVITY: CC Reaction=ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L- CC threonyl-[protein]; Xref=Rhea:RHEA:46608, Rhea:RHEA-COMP:11060, CC Rhea:RHEA-COMP:11605, ChEBI:CHEBI:15378, ChEBI:CHEBI:30013, CC ChEBI:CHEBI:30616, ChEBI:CHEBI:61977, ChEBI:CHEBI:456216; CC EC=2.7.11.1; CC -!- CATALYTIC ACTIVITY: CC Reaction=ATP + H2O = ADP + H(+) + phosphate; Xref=Rhea:RHEA:13065, CC ChEBI:CHEBI:15377, ChEBI:CHEBI:15378, ChEBI:CHEBI:30616, CC ChEBI:CHEBI:43474, ChEBI:CHEBI:456216; CC -!- COFACTOR: CC Name=Mg(2+); Xref=ChEBI:CHEBI:18420; CC Note=Binds 2 Mg(2+) ions per subunit, one in each domain. Mg(2+) is CC required for hexamerization and phosphatase activity. CC -!- SUBUNIT: Homohexamer; hexamerization is dependent on ATP-binding. CC Component of the KaiBC complex. KaiC interacts with SasA, CC activating its autokinase function and leading to RpaA activation. CC -!- DOMAIN: In the homohexamer the 2 domains (called CI and CII) self- CC associate to each form a 'donut' layer; the compactness and local CC conformation of the domains varies over the cell cycle and impacts CC function. CII has the autokinase and autophosphatase activities, both CC CI and CII have (weak) ATPase activity; CI has the clock pacemaker CC role. CC -!- PTM: Phosphorylated on serine and threonine residues by autocatalysis. CC Has a 4 step phosphorylation cycle; the autokinase acts first on #{Thr- CC 432}, then #{Ser-431}. When #{Ser-431} is modified KaiC switches to an CC autophosphatase mode, acting first on phospho-#{Thr-432} then CC phospho-#{Ser-431}. CC -!- MISCELLANEOUS: The kiaA gene has been eliminated from Prochlorococcus CC during genome streamlining. It has been suggested that the central CC oscillator in Prochlorococcus does not have to be as robust as in other CC cyanobacteria because the former live in specific niches of the Earth's CC oceans; they divide exactly once a day and at the same time. Thus gene CC loss, and changes in kaiC function compared to other cyanobacteria, can CC occur. end case CC -!- SIMILARITY: Belongs to the KaiC family. XX DR PROSITE; PS51146; KAIC; 2; trigger=no DR Pfam; PF06745; KaiC; 1; trigger=no DR NCBIfam; TIGR02655; circ_KaiC; 1; trigger=no XX KW ATP-binding KW Nucleotide-binding KW Biological rhythms KW Hydrolase KW Magnesium KW Metal-binding case KW Phosphoprotein end case KW Repeat KW Repressor KW Kinase KW Serine/threonine-protein kinase KW Transcription KW Transcription regulation KW Transferase XX GO GO:0000287; F:magnesium ion binding GO GO:0004712; F:protein serine/threonine/tyrosine kinase activity GO GO:0005524; F:ATP binding GO GO:0007623; P:circadian rhythm XX FT From: KAIC_SYNE7 (Q79PF4) FT DOMAIN 1..247 FT /note="KaiC 1" FT DOMAIN 261..Cter FT /note="KaiC 2" FT BINDING 49 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="1" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: G FT BINDING 50 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="1" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: T FT BINDING 51 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="1" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: G FT BINDING 52 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="1" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: K FT BINDING 53 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="1" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: T FT BINDING 53 FT /ligand="Mg(2+)" FT /ligand_id="ChEBI:CHEBI:18420" FT /ligand_label="1" FT Condition: T FT BINDING 54 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="1" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: L FT BINDING 89 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="1" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: S FT BINDING 224 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="1" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: K FT BINDING 225 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="1" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: L FT BINDING 226 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="1" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: R FT BINDING 228 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="1" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: T FT BINDING 230 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="1" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: H FT BINDING 240 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="1" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: T FT BINDING 241 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="1" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: D FT BINDING 290 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: T FT BINDING 291 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: G FT BINDING 292 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: T FT BINDING 293 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: G FT BINDING 294 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: K FT BINDING 295 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: T FT BINDING 295 FT /ligand="Mg(2+)" FT /ligand_id="ChEBI:CHEBI:18420" FT /ligand_label="2" FT Condition: T FT BINDING 296 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: L FT BINDING 318 FT /ligand="Mg(2+)" FT /ligand_id="ChEBI:CHEBI:18420" FT /ligand_label="2" FT Condition: E FT BINDING 331 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: W FT BINDING 451 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: R FT BINDING 457 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: K FT BINDING 458 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: M FT BINDING 459 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: R FT BINDING 461 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: S FT BINDING 463 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: H FT BINDING 465 FT /ligand="ATP" FT /ligand_id="ChEBI:CHEBI:30616" FT /ligand_label="2" FT /ligand_note="ligand shared between homodimeric partners" FT Condition: K FT MOD_RES 431 FT /note="Phosphoserine; by autocatalysis" FT Tag: phospho; Condition: S FT MOD_RES 432 FT /note="Phosphothreonine; by autocatalysis" FT Tag: phospho; Condition: T XX Size: 499-541; Related: None; Template: Q79PF4; Q79V60; P74646; Q7V0C4; Scope: Bacteria; Cyanobacteriota Fusion: Nter: None Cter: None Duplicate: None Plasmid: None Comments: Prochlorococcus do not contain KaiA (which stimulates KaiC autophosphorylation activity), suggesting that regulation of circadian cycle is different in these bacteria. XX # Revision 1.28 2023/06/01 //