Transport of proteins into chloroplasts. Partial purification of a thylakoidal processing peptidase involved in plastocyanin biogenesis.
Plastocyanin is synthesized in the cytoplasm as a larger precursor and transported across three membranes into the chloroplast thylakoid lumen. Processing to the mature size involves successive cleavages by a stromal and a thylakoidal peptidase. In this report we describe the partial purification and characterization of the thylakoidal peptidase involved. The enzyme has been purified 36-fold from Pisum sativum thylakoids after solubilization using Triton X-100. The peptidase processes the plastocyanin import intermediate to the mature size, but no further, and is capable of processing pre-plastocyanin to the mature size but at a lower rate. No detectable activity is displayed against non-chloroplast proteins or precursors of stromal proteins. The enzyme has a pH optimum of 6.5-7 and is activated by chelating agents such as EDTA and EGTA. No inhibitors of the peptidase have been found to date.
Kirwin
P M
PM
Department of Biological Sciences, University of Warwick, Coventry, Great Britain.
Elderfield
P D
PD
Robinson
C
C
D001693:Biological Transport, Active; D002736:Chloroplasts / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D010447:Peptide Hydrolases / Q000302:isolation & purification* / Q000378:metabolism; D010940:Plant Proteins / Q000096:biosynthesis* / Q000378:metabolism*; D010944:Plants / Q000201:enzymology; D010970:Plastocyanin / Q000096:biosynthesis*
D010940:Plant Proteins; D010970:Plastocyanin; D010447:Peptide Hydrolases