Single point mutations in the small cytoplasmic loop of ACA8, a plasma membrane Ca2+-ATPase of Arabidopsis thaliana, generate partially deregulated pumps.

ABSTRACT: ACA8 is a type 2B Ca(2+)-ATPase having a regulatory N terminus whose auto-inhibitory action can be suppressed by binding of calmodulin (CaM) or of acidic phospholipids. ACA8 N terminus is able to interact with a region of the small cytoplasmic loop connecting transmembrane domains 2 and 3. To determine the role of this interaction in auto-inhibition we analyzed single point mutants produced by mutagenesis of ACA8 Glu(252) to Asn(345) sequence. Mutation to Ala of any of six tested acidic residues (Glu(252), Asp(273), Asp(291), Asp(303), Glu(302), or Asp(332)) renders an enzyme that is less dependent on CaM for activity. These results highlight the relevance in ACA8 auto-inhibition of a negative charge of the surface area of the small cytoplasmic loop. The most deregulated of these mutants i

SUBMITTER: Fusca T 

PROVIDER: S-EPMC2781487 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature