Age-related changes in human lens crystallins identified by two-dimensional electrophoresis and mass spectrometry.
The purpose of this study was to identify the major protein components in adult human lenses and to analyse the specific age-related changes in these proteins using two-dimensional electrophoresis, Edman sequencing, and in conjunction with the data in the accompanying manuscript, mass spectrometry. The majority of changes in the two-dimensional electrophoretic pattern of lens proteins occurred prior to 17 years of age, and included a decrease in proteins migrating to the original positions of beta B1, beta B3, beta A3, gamma C and gamma D, and the appearance of many new species with apparent molecular weights on two-dimensional electrophoretic gels similar to beta B2 and gamma S, but having more acidic pIs. These proteins were identified as deamidated forms of beta B1 and beta A3/A1 missing portions of their N-terminal extensions. With the exception of alpha B, deamidation was detected in all crystallin species. These data indicated that a major fraction of the water-soluble protein of the adult human lens is composed of truncated beta B1 and beta A3/A1 crystallins, and that nearly all human crystallins, including the, beta-crystallins, are susceptible to deamidation. The results also provided the most detailed map to date of the identities of protein species on two-dimensional electrophoresis gels of adult human lenses.
Lampi
K J
KJ
Department of Oral Molecular Biology, Oregon Health Sciences University, Portland 97201, USA.
Ma
Z
Z
Hanson
S R
SR
Azuma
M
M
Shih
M
M
Shearer
T R
TR
Smith
D L
DL
Smith
J B
JB
David
L L
LL
D000293:Adolescent; D000375:Aging / Q000378:metabolism*; D002386:Cataract / Q000378:metabolism; D002675:Child, Preschool; D003459:Crystallins / Q000737:chemistry*; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D007223:Infant; D007908:Lens, Crystalline / Q000737:chemistry / Q000196:embryology*; D013058:Mass Spectrometry; D008875:Middle Aged
D003459:Crystallins