Abstract
Hsp90 plays important roles in diverse pathways in eukaryote. However, functions of its prokaryotic counterpart HtpG are not understood. In cyanobacteria, we reported previously that HtpG protein increased in response to various stress conditions such as heat, high light, oxidation and iron-deficiency. In addition, htpG null mutant revealed reduced production of phycocyanin and chlorophyll.
Our systematic analysis of protein-protein interactions by using yeast two-hybrid analysis suggested a specific interaction between HtpG and HemE (uroporphyrinogen decarboxyrase). HemE is a key enzyme in that its activity facilitates the porphyrin and chlorophyll metabolism. To analyse the role of HtpG in the HemE activity, the cell lysate of ΔhtpG strain was assayed and compared to that of the wild type strain by measuring the level of uroporphyrin. The results indicated that the enzymatic activity of HemE was higher in the htpG mutant suggesting a negative effect of HtpG on HemE activity.
