title: In search of circular permuted variants of Escherichia coli dihydrofolate reductase.
abstract: A circularized form of a Cys-free mutant of Escherichia coli dihydrofolate reductase (DHFR) was used to search for a proteolytic site that gave new N- and C-termini on circularized DHFR with enzyme activity. Of the six site-specific proteolytic enzymes tested, three proteases, Achromobacter protease I (lysine-specific endopeptidase), asparaginylendopeptidase, and Staphylococcus aureus V8 protease, cleaved a single site of the circularized DHFR to form circular permuted variants. Twenty-four possible sites for cleavage were found formation of eight circular permuted variants was suggested by results of N-terminal sequence analysis of the linearized proteins isolated by gel filtration in the presence of 5 M guanidine hydrochloride. Mapping of the predicted cleavage sites on the DHFR molecule suggested that they were not all at a specific loop and, therefore, there are many possible circular permuted variants.
authors.affiliation: National Institute of Bioscience and Human Technology, Ibaraki, Japan. iwakura@nibh.go.jp
authors.forename: M
authors.initials: M
authors.lastname: Iwakura
mesh_terms: D000595:Amino Acid Sequence; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology*; D006868:Hydrolysis; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry / Q000378:metabolism*
chemical_list: D007527:Isoenzymes; D013762:Tetrahydrofolate Dehydrogenase