Abstract:
:We present a quantitative analysis of conformational changes of the nucleotide-binding subunits, MalK(2), of the maltose ATP-binding cassette importer MalFGK(2) during the transport cycle. Distance changes occurring between selected residues were monitored in the full transporter by site-directed spin-labeling electron paramagnetic resonance spectroscopy and site-directed chemical cross-linking. We considered S83C and A85C from the conserved Q-loop and V117C located on the outer surface of MalK. Additionally, two native cysteines (C350, C360) were included in the study. On ATP binding, small rearrangements between the native sites, and no distance changes between positions 117 were detected. In contrast, positions 85 come closer together in the ATP-bound state and in the vanadate-trapped intermediate and move back toward the apo-state after ATP hydrolysis. The distance between positions 83 is shown to slightly decrease on ATP binding, and to further decrease after ATP hydrolysis. Results from cross-linking experiments are in agreement with these findings. The data are compared with in silico spin-labeled x-ray structures from both isolated MalK(2) and the MalFGK(2)-E complex. Our results are consistent with a slightly modified "tweezers-like" model of closure and reopening of MalK(2) during the catalytic cycle, and show an unforeseen potential interaction between MalK and the transmembrane subunit MalG.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Grote M,Bordignon E,Polyhach Y,Jeschke G,Steinhoff HJ,Schneider Edoi
10.1529/biophysj.108.132456subject
Has Abstractpub_date
2008-09-15 00:00:00pages
2924-38issue
6eissn
0006-3495issn
1542-0086pii
S0006-3495(08)78434-0journal_volume
95pub_type
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