The importance of the C-terminal region and Cys residues for the membrane association of the NADPH : protochlorophyllide oxidoreductase in pea

In vitro chloroplast import reactions and thylakoid association reactions h ave been performed with a series of C-terminal deletions and Cys-to-Ser sub stitution mutants of the pea NADPH:protochlorophyllide oxidoreductase (POR; EC 1.6.99). C-terminal deletions of the precursor POR (Delta 362-400, Delt a 338-400, Delta 315-400 and Delta 300-400) were efficiently translocated a cross the chloroplast envelope. However, except the Delta 396-400 mutant, n o C-terminal deletion mutants or Cys-to-Ser substitution (Cys119, Cys281 an d Cys309) mutants resisted posttreatment with thermolysin after the thylako id association reactions. This suggests that these mutants were unable to p roperly associate to the thylakoids due to changes of the protein conformat ion of POR. (C) 2001 Federation of European Biochemical Societies. Publishe d by Elsevier Science B.V. All rights reserved.