Yeast l ‐Lactate Dehydrogenase (Cytochrome b2)

As has been known for some time, proteolysis of cytochrome b2 yields a small protein fragment (cytochrome b2 core) which still carries the heme. This paper describes the separation of the various bands which can be seen upon electrophoresis of the small hemoprotein. The isoelectric points of the two main bands are 6.40 and 5.55. Amino acid analyses show that they have about 80 and 100 residues, respectively. End group studies using in particular carboxypeptidase C demonstrated that both bands have lysine as N‐ and C‐terminal residues. Altogether, the data indicated that the various bands come from splits of the main chain at different positions. The significance of these results is discussed in relation with what is currently known about the structure of cytochrome b2.