A protein methylase III responsible for specifically methylating the cytochrome 
c in Neurospora crassa was partially characterized by using unmethylated horse 
heart cytochrome c as a substrate. This enzyme utilizes S-adenosyl-L-methionine 
as the methyl donor. An analysis of the distribution of [14C]methyl groups in 
the peptides obtained by chymotrypsin digestion of the enzymically methylated 
cytochrome c showed that all of the radioactivity could be recovered within a 
single peak after chromatography. This indicates that the enzyme methylates a 
specific amino acid sequence within cytochrome c. On hydrolysis of the 
radioactive chymotryptic peptide, Me-14C-labelled epsilon -N-mono-methyl-lysine, 
epsilon-N-dimethyl-lysine and epsilon-N-trimethyl-lysine were identified. The 
enzyme can easily be extracted from the N. crassa mycelial pads and was purified 
approx. 30-fold.