Abstract
HCF164 is a membrane anchored thioredoxin-like protein faced to thylakoid lumen side. In this study, we found that chloroplast stroma m-type thioredoxin is the source of reducing equivalents for reduction of HCF164 in the thylakoid lumen. In order to probe the function of HCF164 in the lumen, we screened the reducing equivalent acceptor proteins of HCF164 using a resin-immobilized HCF164-single cysteine mutant, and successfully identified the putative target thylakoid proteins. Among the newly identified target protein candidates, the reduction of the PSI-N subunit of photosystem I by HCF164 was confirmed both in vitro and in isolated thylakoids. Two components of the cytochrome b6f complex, the cytochrome f and Rieske FeS proteins, were also captured as novel potential target proteins by our chromatography method. We will discuss the physiological role of HCF164 in the thylakoid lumen.
