AMINO-ACID-SEQUENCE OF BOVINE GAMMA-E(IVA) LENS CRYSTALLIN

When electrospray ionization mass spectrometry (ES-MS) was used to ana lyze purified bovine gamma E (gamma IVa)-crystallin, it yielded a rela tive molecular mass (M(r)) of 20,955 +/- 5. This mass is significantly different from that calculated from the published sequence (M(r) 20,8 94) (White HE et al., 1989, J Mol Biol 207:217-235). Further, ES-MS an alysis of the protein after it had been reduced and carboxymethylated indicated the presence of five cysteine residues, whereas the publishe d sequence contains six (Kilby GW et al., 1995, fur Mass Spectrom 1:20 3-208). The entire protein sequence of gamma E crystallin has therefor e been studied via a combination of ES-MS, ES-MS/MS, and Edman amino a cid sequencing. The corrected sequence gives an M(r) of 20,955.3, whic h matches that obtained by ES-MS analysis of the purified native prote in. The corrected sequence is also in agreement with a recent cDNA seq uence obtained for a bovine gamma-crystallin by R. Hay (pers. comm.).