High resolution structures of wild type and apo human CuZn superoxide dismutase and its fals-related mutants

Abstract

4 Fukuoka Dental College 8-Oxoguanine is produced in the chromosomal DNA, RNA and free nucleotides such as dGTP and GTP by active oxygen species usually formed during cellular metabolic processes. 8-Oxoguanine can mispair with adenine during replication and transcription. Escherichia coli MutT protein prevents replicational and transcriptional errors by hydrolysis of potent mutagenic substrates for DNA and RNA syntheses, 8-oxo-dGTP and 8-oxo-GTP to the corresponding nucleoside monophosphates. Our research purpose is to get detailed insights into the specific recognition for the 8-oxoguanine base and the catalytic mechanism for the hydrolysis of 8-oxo-dGTP and 8-oxo-GTP by the MutT protein. In this study, we have determined the crystal structures of E. coli MutT proteins with and without manganese ions. First, the structure of apo MutT was solved by the MAD method using selenomethionyl MutT protein. Second, the structure of MutT-metal complex was solved by the molecular replacement method using the apo MutT structure. The overall structure of MutT consists of an α + β fold with 6-stranded β-sheet sandwiched between the two α-helices. Three manganese ions bind to a glutamate cluster in Nudix motif (GX5EX7REUXEEXGU) with no significant conformational changes compared with apo MutT.