SECONDARY MODIFICATION OF CYTOCHROME C BY NEUROSPORA CRASSA

Two molecular species of cytochrome c, CI and CII, were detected in Neurospora crassa. The two cytochrome c’s differ in structure at residue 72. This position is occupied by lysine in CII. The equivalent residue in CI, a lysine derivative, has been identified as ϵ-trimethyllysine (DeLange, J. R., Glazer, A. N., and Smith, E. L. (1969), J. Biol. Chem. 244, 1385). A sequential synthesis of the two cytochrome c’s occurs in Neurospora cultures. Pulse-chase experiments with [14C]lysine indicate that CII, the early cytochrome c, is converted into CI presumably by a specific methylation of lysine-72 in CII to give ϵ-trimethyllysine in CI. The kinetics of CI and CII synthesis in the poky mutant also suggest that the conversion of CII into CI reflects the binding of the cytochrome c to the mitochondrion. © 1969, American Chemical Society. All rights reserved.