Characterization and functional analysis of the nucleotide binding fold inhuman peroxisomal ATP binding cassette transporters

The 70-kDa peroxisomal membrane protein (PMP70) and the adrenoleukodystroph y protein (ALDP) are half ATP binding cassette (ABC) transporters in the pe roxisome membrane. Mutations in the ALD gene encoding ALDP result in the X- linked neurodegenerative disorder adrenoleukodystrophy. Plausible models ex ist to show a role for ATP hydrolysis in peroxisomal ABC transporter functi ons. Here, we describe the first measurements of the rate of ATP binding an d hydrolysis by purified nucleotide binding fold (NBF) fusion proteins of P MP70 and ALDP, Both proteins act as an ATP specific binding subunit releasi ng ADP after ATP hydrolysis; they did not exhibit GTPase activity. Mutation s in conserved residues of the nucleotidases (PMP70: G478R, S572I; ALDP: G5 12S, S606L) altered ATPase activity. Furthermore, our results indicate that these mutations do not influence homodimerization or heterodimerization of ALDP or PMP70, The study provides evidence that peroxisomal ABC transporte rs utilize ATP to become a functional transporter. (C) 2001 Federation of E uropean Biochemical Societies. Published by Elsevier Science B.V. All right s reserved.