Biochemical properties of rice adenylate kinase and subcellular location in plant cells.

Previously, we characterized nucleotide sequences of two cDNAs encoding adenylate kinase from rice plants (Oryza sativa L.). Each cDNA (Adk-a or Adk-b) was cloned into the expression vector pET 11d-GST to produce GST-AK fusion proteins in Escherichia coli. Recombinant proteins were cleaved by thrombin, and GST-free adenylate kinase proteins were obtained. Enzyme activity profiles of different pH and inhibition effects to the enzyme by Ap5A (adenosine-5'-pentaphospho-5'-adenosine) indicates that both adenylate kinase proteins have similar biochemical characteristics. Among the nucleoside monophosphates (AMP, CMP, GMP and UMP) investigated, only AMP reacted with ATP. Furthermore, using the antiserum against the rice adenylate kinase proteins, the cellular location of adenylate kinase proteins was examined by immunomicroscopic analysis in combination with a subcellular fractionation method. The results indicated that adenylate kinase proteins were distributed largely in cytosol of rice cells.