Multiple Molecular Forms of Chorismate Mutase in Bacillus subtillis

Abstract

Two genetically related strains of Bacillus subtilis differ in the number of molecular forms of chorismate mutase (CM) they express. Strain 23 and its derivatives have three distinct species separable on DEAE-cellulose, termed CM1, CM2, and CM3. Strain 168 has only the CM3 form. The locus concerned with CM3 synthesis has been separated from the locus (i) concerned with CM1 and CM2 synthesis by genetic recombination. The present data are most compatible with only one locus being concerned with CM1 and CM2 formation. Since rechromatography of the CM2 species (mol wt 140,000) on DEAE-cellulose results in the appearance of the CM1 moiety (mol wt 75,000), CM1 and CM2 may represent different aggregational states involving at least one common subunit. CM1 and CM3 differ markedly in a number of physical properties, including molecular weight, heat stability, substrate affinity, and chromatographic properties. Neither CM1 nor CM3 activity is inhibited in vitro by the aromatic amino acids. The significance of these multiple forms to the biosynthesis of aromatic amino acids is discussed. © 1967, American Chemical Society. All rights reserved.