抄録
FtsH is an ATP-dependent metalloprotease and present as a hetero-complex in thylakoid membranes. FtsH2, encoded in Arabidopsis VAR2 locus, is a major isoform. Lack of FtsH2 results in a typical leaf-variegated phenotype. While we have identified more than 20 var2 alleles, none of the mutations was found in the catalytic center of protease activity (comprised by zinc-binding domain). To test the importance of this domain, we replaced one of the essential histidine residues in the domain with leucine, and over expressed it in var2. We found that this mutation in E. coli FtsH abolishes protease activity in vivo, and that the mutated FtsH2 rescued the variegated phenotype in var2. The result implies that the protein level rather than the protease activity determines leaf variegation. Loss of the protease activity may be mitigated by other isoforms of the FtsH complex. Experiments to clarify these observations are currently underway.
