[Characteristics of isoforms of Serratia marcescens from electrospray mass spectrometry]

Electrospray mass spectrometry was used to determine the molecular masses of nuclease isoforms isolated and purified from the cultural fluid of Serratia marcescens B10M1. The primary structure of each of the isoforms isolated from the nuclease preparations was established by comparing their masses with the known amino acid sequence encoded by the nuc-gene. The structure of some of these isoforms was verified by N-terminal sequencing, that of nearly all isoforms-by isoelectric focusing. All nuclease isoforms were found to be variants of native nuclease split at the molecular N-termini.