Based on the present literature, it is unclear whether betaB2-crystallin undergoes age-related truncation in human lenses. To answer this question, the purpose of this study was to determine in vivo truncation of betaB2-crystallin in human lenses during aging by examining its fragments in the beta(H)-crystallin fraction. The WS-protein fraction was isolated from lenses of desired ages and separated by a size-exclusion Agarose A 1.5 m column to recover alpha-, beta(H)-, beta(L)-, and gamma-crystallin fractions. The beta(H)-crystallin fractions, isolated from lenses of 24- and 70-year-old donors, were utilized for two-dimensional (2D) gel electrophoresis (isoelectric focusing in the first dimension followed by SDS-PAGE in the second dimension). The partial N-terminal sequences of the desired fragments (Molecular weights [M,] < 18-19kDa) from a 2D-gel of WS-proteins from lenses of a 70-year-old donor were determined. More than 37 crystallin fragments with M-r between 4 and 19 kDa were observed on a 2D-gel. Nine fragments in beta(H)-crystallin fraction were from betaB2-crystallin but additional single fragments of alphaA-, gammas-, betaA4, and of either gammaB-, gammaC- or gammaD-crystallins were also observed. Seven cleavage sites in the betaB2-crystallin were identified, which included two sites at Q(7)-A(8) and A(8)-G(9) bonds in the N-terminal extension, two sites at E-46-K-47 and G(49)-S-50 bonds in the motif 1, one site at S-94-S-95 in the motif 2, and two sites at N-115-F-116 and Q(115)-Y-136 in motif 3. No fragments with cleavage in the motif 4 and C-terminal extension of betaB2-crystallin were seen. Apparently, three betaB2-crystallin fragments with only N-terminal cleavage and five with both N- and C-terminal cleavages were observed. Additional fragments with cleavage sites at Q(54)-Y-55 in alphaA-crystallin, at E-112-N-113 in betaA4-crystallin, at G(4)-T-5 in gammas-crystallin, at M-69-G(70) in either gammaB-, gammaC- or gammaD-crystallins (three have identical sequences at the cleaved bond), and at G(1)-K-2 in gammaB or gammaC (both have identical sequences at the cleavage site) were observed. Conclusions. The results showed that betaB2-crystallin undergoes age-related truncation producing fragments with M, between 4 and 19 kDa that existed in the beta(H)-crystallin oligomer. The beta(H)-crystallin fraction also contained single fragments of alpha-, betaA4-, gammas-, and other gamma-crystallins. (C) 2002 Elsevier Science (USA). All rights reserved.