Journal
JOURNAL OF MOLECULAR BIOLOGY
Volume 325, Issue 2, Pages 259-274Publisher
ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD
DOI: 10.1016/S0022-2836(02)01105-1
Keywords
ABC transporter; sequence alignment; homology; phylogeny; evolution
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An alignment of the mammalian ABCA transporters enabled the identification of sequence segments, specific to the ABCA subfamily, which were used as queries to search for eukaryotic and prokaryotic homologues. Thirty-seven eukaryotic half and full-length transporters were found, and a close relationship with prokaryotic subfamily 7 transporters was detected. Each half of the ABCA full-transporters is predicted to comprise a membrane-spanning domain (MSD) composed of six helices and a large extracellular loop, followed by a nucleotide-binding domain (NBD) and a conserved cytoplasmic 80-residue sequence, which might have a regulatory function. The topology predicted for the ABCA trans porters was compared to the crystal structures of the MsbA and BtuCD bacterial transporters. The alignment of the MSD and NBD domains provided an estimate of the degree of residue conservation in the cytoplasmic, extracellular and transmembrane domains of the ABCA trans porter subfamily. The phylogenic tree of eukaryotic ABCA transporters based upon the NBD sequences, consists of three major clades, corresponding to the half-transporter single NBDs and to the full-transporter NBD1s and NBD2s. A phylogenic tree of prokaryotic transporters and the eukaryotic ABCA transporters confirmed the evolutionary relationship between prokaryotic subfamily 7 transporters and eukaryotic ABCA half and full-transporters. (C) 2003 Elsevier Science Ltd. All rights reserved.
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