The length of the A-M3 linker is a crucial determinant of the rate of the Ca2+ transport cycle of sarcoplasmic reticulum Ca2+-ATPase.

ABSTRACT: Ion translocation by the sarcoplasmic reticulum Ca(2+)-ATPase depends on large movements of the A-domain, but the driving forces have yet to be defined. The A-domain is connected to the ion-binding membranous part of the protein through linker regions. We have determined the functional consequences of changing the length of the linker between the A-domain and transmembrane helix M3 ("A-M3 linker") by insertion and deletion mutagenesis at two sites. It was feasible to insert as many as 41 residues (polyglycine and glycine-proline loops) in the flexible region of the linker without loss of the ability to react with Ca(2+) and ATP and to form the phosphorylated Ca(2)E1P intermediate, but the rate of the energy-transducing conformational transition to E2P was reduced by >80%. Insertion of a sm

SUBMITTER: Holdensen AN 

PROVIDER: S-EPMC2673294 | biostudies-literature | 2009 May

REPOSITORIES: biostudies-literature