Abstract
The main function of FtsH protease in plant cell is quality control of membrane protein. D1 protein in photosystem II is one of the main targets of FtsH protease, because D1 protein is easily damage during the photosynthesis. FtsH protease participates in this turnover. FtsH protease is an ATP dependent metalloprotease and is composed from the following three domains; transmembrane, ATPase and protease domain. We constructed over-expression system of protease domain in FtsH from tobacco. Protein was collected as inclusion body. It was activated by urea denatured and dialyzed. We used FITC (fluorescein isothiocyanate)-casein for substrate protein. Biochemical analysis revealed that the activity was stimulated by higher concentration of magnesium ion, and pH optimum showed alkalescent condition. Beta-casein was selectively digested, though alpha-casein, bovine serum albumin, or Rubisco was not degraded by the protease domain. Cleavage site of this digested beta-casein clarified by peptide sequencing.
