Functional Analysis of HCF164, a Thioredoxin-Like Protein in the Thylakoid Lumen

Abstract

HCF164 is a thylakoid membrane-anchored thioredoxin-like protein, which was initially found by the analysis of the chlorophyll fluorescence mutant Arabidopsis. Whereas the thioredoxin-like domain of HCF164 is located in the thylakoid lumen and the active cysteine residues of HCF164 face to thylakoid luminal side, the knowledge on a disulfide-dithiol redox control system is very limited in the thylakoid lumen. To study the function of HCF164 in the thylakoid lumen, we have developed the monitoring system for redox states of HCF164 in thylakoids. Using this assay system, we have found that chloroplast stroma m-type thioredoxin is the most probable source of reducing equivalents for HCF164. The results of our study clearly show that higher plant chloroplast possess a trans-membrane reducing equivalent transfer system.