Some aspects of carboxyl-terminal processing of precursor D1 protein in photosystem II

Abstract

The carboxyl-terminal processing of precursor D1 protein (pD1), which is an essential process in the functional integration of Mn-cluster in photosystem II, is a typical example of nuclear regulation of chloroplast gene expression at the level of post-translation in eukaryotic organisms. The nuclear-encoded enzyme (CtpA) involved in this process has been purified and its three-dimensional structure has been determined. This enzyme is classified into a novel type of serine protease, as also shown by our recent results on its inhibitor specificity and the site-directed mutational analysis (collaboration with Pakrasi¿s group). On the other hand, approximately a hundred of deduced sequence data are now available on the substrate pD1 for a wide variety of organisms ranging from prokaryotic cyanobacteria to higher plants. Recently, unique sequences of pD1 for dinoflagellates have been provided. We have investigated this proteolytic process from both the enzyme and the substrate using systems of different integrities in order to understand the mechanism of functional expression of the water-splitting machinery in photosystem II. In this poster, we will discuss some aspects of enzyme-substrate interaction in the carboxyl-terminal processing of pD1 in thylakoidal lumen, and speculate about the evolution of nuclear regulation of this process.