The β subunit loop that couples catalysis and rotation in ATP synthase has a critical length

Nelli Mnatsakanyan, Silas K. Kemboi, Jasmin Salas, Joachim Weber

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

ATP synthase uses a unique rotational mechanism to convert chemical energy into mechanical energy and back into chemical energy. The helix-turn-helix structure in the C-terminal domain of the β subunit containing the conserved DELSEED motif, termed "DELSEED-loop," was suggested to be involved in coupling between catalysis and rotation. If this is indeed the role of the loop, it must have a critical length, the minimum length required to sustain its function. Here, the critical length of the DELSEED-loop was determined by functional analysis of mutants of Bacillus PS3 ATP synthase that had 7-14 amino acids within the loop deleted.A10 residue deletion lost the ability to catalyze ATP synthesis, but was still an active ATPase. Deletion of 14 residues abolished any enzymatic activity. Modeling indicated that in both deletion mutants the DELSEEDloop was shortened by ∼10Å fluorescence resonance energy transfer experiments confirmed the modeling results. This appears to define the minimum length for DELSEED-loop required for coupling of catalysis and rotation. In addition, we could demonstrate that the loss of high-affinity binding to the catalytic site(s) that had been observed previously in two deletion mutants with 3-4 residues removed was not due to the loss of negative charged residues of the DELSEED motif in these mutants. An AALSAAA mutant in which all negative charges of the DELSEED motif were removed showed a normal pattern for MgATP binding to the catalytic sites, with a clearly present high-affinity site.

Original languageEnglish
Pages (from-to)29788-29796
Number of pages9
JournalJournal of Biological Chemistry
Volume286
Issue number34
DOIs
StatePublished - Aug 26 2011

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