ID   CARH_MYXXA              Reviewed;         299 AA.
AC   Q50900;
DT   11-JUN-2014, integrated into UniProtKB/Swiss-Prot.
DT   09-JAN-2007, sequence version 2.
DT   03-AUG-2022, entry version 106.
DE   RecName: Full=HTH-type transcriptional repressor CarH;
GN   Name=carH;
OS   Myxococcus xanthus.
OC   Bacteria; Proteobacteria; Deltaproteobacteria; Myxococcales;
OC   Cystobacterineae; Myxococcaceae; Myxococcus.
OX   NCBI_TaxID=34;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RC   STRAIN=DK1050;
RX   PubMed=7588751; DOI=10.1111/j.1432-1033.1995.238_1.x;
RA   Botella J.A., Murillo F.J., Ruiz-Vazquez R.M.;
RT   "A cluster of structural and regulatory genes for light-induced
RT   carotenogenesis in Myxococcus xanthus.";
RL   Eur. J. Biochem. 233:238-248(1995).
RN   [2]
RP   FUNCTION, DNA-BINDING, ACTIVITY REGULATION, SUBUNIT, INTERACTION WITH CARS,
RP   DOMAIN, GENE NAME, AND MUTAGENESIS OF ARG-42 AND HIS-193.
RC   STRAIN=DK1050;
RX   PubMed=18315685; DOI=10.1111/j.1365-2958.2007.06086.x;
RA   Perez-Marin M.C., Padmanabhan S., Polanco M.C., Murillo F.J.,
RA   Elias-Arnanz M.;
RT   "Vitamin B12 partners the CarH repressor to downregulate a photoinducible
RT   promoter in Myxococcus xanthus.";
RL   Mol. Microbiol. 67:804-819(2008).
RN   [3]
RP   ACTIVITY REGULATION.
RC   STRAIN=DK1050;
RX   PubMed=21502508; DOI=10.1073/pnas.1018972108;
RA   Ortiz-Guerrero J.M., Polanco M.C., Murillo F.J., Padmanabhan S.,
RA   Elias-Arnanz M.;
RT   "Light-dependent gene regulation by a coenzyme B12-based photoreceptor.";
RL   Proc. Natl. Acad. Sci. U.S.A. 108:7565-7570(2011).
CC   -!- FUNCTION: Negative regulator of the carB operon in the dark. Binds
CC       specifically to the CarA operator, in the region around the carB
CC       promoter, which blocks access to the RNA polymerase.
CC       {ECO:0000269|PubMed:18315685}.
CC   -!- ACTIVITY REGULATION: Requires cobalamin (vitamin B12) for repressor
CC       activity. In the dark, binding of cobalamin to CarH induces its
CC       oligomerization, which enhances binding to the DNA and repressor
CC       activity. Light causes cobalamin photolysis and disruption of the
CC       cobalamin-CarH complex, which decreases interaction with DNA and allows
CC       transcription of the carB operon. Interaction with CarS also prevents
CC       binding to DNA. {ECO:0000269|PubMed:18315685,
CC       ECO:0000269|PubMed:21502508}.
CC   -!- SUBUNIT: Forms oligomers. Interacts with CarS.
CC       {ECO:0000269|PubMed:18315685}.
CC   -!- DOMAIN: The N-terminal region interacts with DNA and CarS, and the C-
CC       terminal region is involved in oligomerization and binding of
CC       cobalamin. {ECO:0000269|PubMed:18315685}.
CC   -!- SIMILARITY: Belongs to the CarA/CarH B12-binding photoregulator family.
CC       {ECO:0000305}.
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DR   EMBL; Z21955; CAA79965.2; -; Genomic_DNA.
DR   PIR; S68198; S68198.
DR   RefSeq; WP_011551025.1; NZ_JABFNQ010000052.1.
DR   AlphaFoldDB; Q50900; -.
DR   SMR; Q50900; -.
DR   PRIDE; Q50900; -.
DR   GeneID; 41358363; -.
DR   OMA; IWEKRYN; -.
DR   GO; GO:0031419; F:cobalamin binding; IEA:InterPro.
DR   GO; GO:0003677; F:DNA binding; IEA:UniProtKB-KW.
DR   GO; GO:0046872; F:metal ion binding; IEA:InterPro.
DR   GO; GO:0008168; F:methyltransferase activity; IEA:UniProt.
DR   GO; GO:0016117; P:carotenoid biosynthetic process; IEA:UniProtKB-KW.
DR   GO; GO:0006355; P:regulation of transcription, DNA-templated; IEA:InterPro.
DR   Gene3D; 1.10.1240.10; -; 1.
DR   InterPro; IPR003759; Cbl-bd_cap.
DR   InterPro; IPR006158; Cobalamin-bd.
DR   InterPro; IPR036724; Cobalamin-bd_sf.
DR   InterPro; IPR009061; DNA-bd_dom_put_sf.
DR   InterPro; IPR000551; MerR-type_HTH_dom.
DR   InterPro; IPR036594; Meth_synthase_dom.
DR   Pfam; PF02310; B12-binding; 1.
DR   Pfam; PF02607; B12-binding_2; 1.
DR   Pfam; PF13411; MerR_1; 1.
DR   SMART; SM00422; HTH_MERR; 1.
DR   SUPFAM; SSF46955; SSF46955; 1.
DR   SUPFAM; SSF52242; SSF52242; 1.
DR   PROSITE; PS51332; B12_BINDING; 1.
DR   PROSITE; PS51337; B12_BINDING_NTER; 1.
DR   PROSITE; PS50937; HTH_MERR_2; 1.
PE   1: Evidence at protein level;
KW   Carotenoid biosynthesis; DNA-binding; Repressor; Transcription;
KW   Transcription regulation.
FT   CHAIN           1..299
FT                   /note="HTH-type transcriptional repressor CarH"
FT                   /id="PRO_0000429423"
FT   DOMAIN          5..74
FT                   /note="HTH merR-type"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00254"
FT   DOMAIN          180..299
FT                   /note="B12-binding"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00666"
FT   DNA_BIND        8..27
FT                   /note="H-T-H motif"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00254"
FT   MUTAGEN         42
FT                   /note="R->A: Lack of activity, even in the presence of
FT                   cobalamin. Retains the ability to interact with CarS."
FT                   /evidence="ECO:0000269|PubMed:18315685"
FT   MUTAGEN         193
FT                   /note="H->A: Lack of activity. Decreases oligomerization."
FT                   /evidence="ECO:0000269|PubMed:18315685"
SQ   SEQUENCE   299 AA;  32929 MW;  FF631C58DF4C0CE9 CRC64;
     MAERTYRINI AAELAGVRVE LIRAWERRYG VLTPRRTPAG YRAYTDRDVA VLKQLKRLTD
     EGVAISEAAK LLPQLMEGLE AEVAGRGASQ DARPHAETWR ESMLAATQAY DQPRVSDVLD
     EVLAALPPLK AFDEVLAPLL CDVGERWESG TLTVAQEHLV SQMVRARLVS LLHAAPLGRH
     RHGVLACFPE EEHEMGLLGA ALRLRHLGVR VTLLGQRVPA EDLGRAVLAL RPDFVGLSTV
     ASRSAEDFED TLTRLRQALP RGLPVWVGGA AARSHQAVCE RLAVHVFQGE EDWDRLAGT