The N-terminus of myosin. I. Studies on N-acetyl peptides from a pronase digest of myosin.

Abstract

The failure of fluorodinitrobenzene to reveal more than traces of N-terminal amino acid in rabbit myosin would be explained if this protein were acetylated at its N-terminus, a situation found in several other proteins. N-acetyl peptides have been sought for and found in a pronase digest of rabbit myosin. These acetyl peptides have been isolated by screening the digest through a sulphonic acid resin and have been separated from each other and from contaminating pyrrolidone carboxylic acid by chromatography on a strong base anion exchange resin (formate form) and subsequent chromatography on thin layers of silica or paper electrophoresis. They unexpectedly do not react with the Rydon-Smith reagent48. They have been identified as N-acetyl-Ser, N-acetyl-Ser-Ser-Asp-Ala-Asp, and a hexapeptide having the amino acid composition Ala, Asp2, Met, Ser2. The yields of peptides obtained indicate that there are at least two polypeptide chains per molecule of rabbit myosin of mol. wt. 600 000 having the N-terminal sequence N-acetyl-Ser-Ser-Asp-Ala-Asp, one at least of which has Met as the next residue.