ABCMdb

PMID: 16171403

Tombline G, Muharemagic A, White LB, Senior AE
Involvement of the "occluded nucleotide conformation" of P-glycoprotein in the catalytic pathway.
Biochemistry. 2005 Sep 27;44(38):12879-86., [PubMed]

Sentences

No. Mutations Sentence Comment

117 ABCB4 p.Ser430Ala E552A/E1197A/S430A and E552A/E1197A/S1073A. Login to comment 120 ABCB4 p.Ser430Ala Previous work has shown (17) that the single mutations S430A and S1073A strongly impair ATPase activity and abolish Vi-trapping of nucleotide in Pgp, although MgATP binding as evaluated by photolabeling with Mg-8-azido-ATP was unimpaired. Login to comment 122 ABCB4 p.Ser430Ala Figure 4 shows that the mutations S430A or S1073A, when combined with E552A/ E1197A, abolished tight binding of MgATP. Login to comment 208 ABCB4 p.Ser430Ala The mutants S430A and S1073A at the loci of the Walker A Ser residues in Pgp remove the hydroxyl side chain known to coordinate to the Mg cation of bound MgATP and MgADP in many nucleotide-binding proteins, including ABC transporters (6, 31-34). Login to comment 209 ABCB4 p.Ser430Ala As noted in the Results, the single mutations S430A and S1073A had been shown previously (17) to inhibit Pgp ATPase activity and transition-state formation (as measured by Vi-ADP trapping) but not to prevent the initial binding of MgATP (as evaluated by 8-azido-ATP labeling), as if the Ser-OH only became tangibly engaged with the Mg-nucleotide at the stage of a "closed conformation". Login to comment 211 ABCB4 p.Ser430Ala Consistent with these data, the mutants E552A/E1197A/S430A and E552A/E1197A/S1073A were deficient in tight binding of MgATP and MgADP (Figures 4 and 5). Login to comment