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3.A.1.107.3
CcmABCD exporter; CcmD (69aas, 1TMS) is required for the release of CcmE (which binds heme in the periplasm) from CcmABC. CcmC (9.B.14.2.3) is required for the transfer of heme to CcmE in the periplasm (Richard-Fogal et al., 2008) In the presence of heme, CcmC and CcmE form a stable complex (Richard-Fogal & Kranz, 2010) as do CcmE and CcmF (San Francisco and Kranz 2014). The cytochrome c maturation system I, consisting of eight membrane/periplasmic proteins (CcmABCDEFGH), results in the attachment of heme to cysteine residues of cytochrome c proteins. Since all c-type cytochromes are periplasmic, heme is first transported to a periplasmic heme chaperone, CcmE. A large membrane complex, CcmABCD has been proposed to carry out this transport and linkage to CcmE. Li et al. 2022 described high resolution cryo-EM structures of CcmABCD in an unbound form, in complex with inhibitor AMP-PNP, and in complex with ATP and heme. The ATP-binding site in CcmA and the heme-binding site in CcmC were identified. They proposed a model of heme trafficking, heme transfer to CcmE, and ATP-dependent release of holoCcmE from CcmABCD. CcmABCD represents an ABC transporter complex using the energy of ATP hydrolysis for the transfer of heme from one binding partner (CcmC) to another (CcmE) (Li et al. 2022).

Accession Number:P0ABM0
Protein Name:CcmB
Length:220
Molecular Weight:23619.00
Species:Escherichia coli O157:H7 [83334]
Number of TMSs:6
Location1 / Topology2 / Orientation3: Cell inner membrane1 / Multi-pass membrane protein2
Substrate ferroheme b

Cross database links:

RefSeq: NP_288780.1    NP_311116.1   
Entrez Gene ID: 916795    957177   
Pfam: PF03379   
BioCyc: ECOL83334:ECS3089-MONOMER   
KEGG: ece:Z3457    ecs:ECs3089   

Gene Ontology

GO:0016021 C:integral to membrane
GO:0005886 C:plasma membrane
GO:0015232 F:heme transporter activity
GO:0017004 P:cytochrome complex assembly
GO:0015886 P:heme transport

References (2)

[1] “Genome sequence of enterohaemorrhagic Escherichia coli O157:H7.”  Perna N.T.et.al.   11206551
[2] “Complete genome sequence of enterohemorrhagic Escherichia coli O157:H7 and genomic comparison with a laboratory strain K-12.”  Hayashi T.et.al.   11258796

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Predict TMSs (Predict number of transmembrane segments)
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FASTA formatted sequence
1:	MMFWRIFRLE LRVAFRHSAE IANPLWFFLI VITLFPLSIG PEPQLLARIA PGIIWVAALL 
61:	SSLLALERLF RDDLQDGSLE QLMLLPLPLP AVVLAKVMAH WMVTGLPLLI LSPLVAMLLG 
121:	MDVYGWQVMA LTLLLGTPTL GFLGAPGVAL TVGLKRGGVL LSILVLPLTI PLLIFATAAM 
181:	DAASMHLPVD GYLAILGALL AGTATLSPFA TAAALRISIQ