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Age-dependent deamidation of the major intrinsic polypeptide from lens membranes
1Division of Biology, Kansas State University, Manhattan 66506.
Abstract:
The Major Intrinsic Polypeptide (MP26) of lens membranes contains an -asn-gly- sequence, which has been shown in other proteins to be particularly susceptible to spontaneous deamidation. To determine if the asparagine residue of this sequence undergoes age-dependent deamidation in vivo, antiserum to a synthetic peptide containing the sequence was used to monitor purification of a tryptic peptide containing this sequence from fetal versus mature bovine lenses. The peptide from fetal lenses contained the -asn-gly- sequence, while the peptide from mature lenses contained an -asp-gly- sequence, demonstrating that age-dependent deamidation of this asparagine residue was occurring in the lens.
Insights
The Major Intrinsic Polypeptide (MP26) in bovine lenses undergoes age-dependent deamidation. This process converts asparagine to aspartic acid in the lens membrane protein, impacting its structure over time.
Area of Science:
- Biochemistry
- Ophthalmology
- Protein Chemistry
Background:
- The Major Intrinsic Polypeptide (MP26) is a key protein in lens membranes.
- A specific asparagine-glycine sequence (-asn-gly-) in MP26 is prone to deamidation.
- Protein deamidation is a post-translational modification that can alter protein function.
Purpose of the Study:
- To investigate whether the asparagine residue in the -asn-gly- sequence of MP26 undergoes age-dependent deamidation in vivo.
- To determine the impact of aging on lens protein integrity.
Main Methods:
- Utilized antiserum against a synthetic peptide containing the -asn-gly- sequence.
- Purified tryptic peptides from fetal and mature bovine lenses.
- Analyzed the sequence of the purified peptides to detect deamidation.
Main Results:
- Peptides from fetal lenses retained the original -asn-gly- sequence.
- Peptides from mature lenses showed the presence of an -asp-gly- sequence.
- This indicates spontaneous deamidation of asparagine occurred with age.
Conclusions:
- Age-dependent deamidation of asparagine in MP26 occurs in the bovine lens.
- This finding contributes to understanding age-related changes in lens proteins.
- Deamidation may play a role in lens aging and associated conditions.