Six-transmembrane helical domain (6TM) of the CydD, a component of the ABC cysteine/GSH transporter, and a homolog AarD
The CydD protein, together with the CydC protein, constitutes a bacterial heterodimeric ATP-binding cassette (ABC) transporter complex required for formation of the functional cytochrome bd oxidase in both gram-positive and gram-negative aerobic bacteria. In Escherichia coli, the biogenesis of both cytochrome bd-type quinol oxidases and periplasmic cytochromes requires the ABC-type cysteine/GSH transporter CydDC, which exports cysteine and glutathione from the cytoplasm to the periplasm to maintain redox homeostasis. Mutations in AarD, a homolog from Providencia stuartii, also show phenotypic characteristic consistent with a defect in the cytochrome d oxidase. The CydDC forms a heterodimeric ABC transporter with two transmembrane domains (TMDs), each predicted to comprise six TM alpha-helices and two nucleotide binding domains (NBDs).
Comment:All members of this ABC transporter family contain 6 alpha-helices in each transmembrane domain (TMD) for a total of 12 TM segments in the complete transporter.
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