Genetics of salivary protein polymorphisms
1University of Wisconsin, Department of Medicine and Medical Genetics, Madison 53706.
Summary
Human salivary proline-rich proteins (PRPs) exhibit diverse genetic polymorphisms due to gene structure and mutations. These variations impact protein processing, dimerization, and gene expression, affecting individual differences in saliva composition.
Area of Science:
- Genetics
- Biochemistry
- Molecular Biology
Background:
- Human salivary proline-rich proteins (PRPs) are encoded by a cluster of six linked genes on chromosome 12p13.2.
- PRPs display complex electrophoretic patterns, indicating significant genetic polymorphism and individual variability.
- Common polymorphisms include length variations and null mutations.
Purpose of the Study:
- To investigate the common themes underlying the diverse polymorphisms observed in human salivary PRPs.
- To understand how genetic variations and molecular mechanisms contribute to PRP diversity.
Main Methods:
- Analysis of electrophoretic patterns of salivary PRPs.
- Identification of genetic variations including mutations, gene rearrangements, and post-translational modifications.
- Examination of gene structure and function within the PRP gene cluster.
Main Results:
- Post-translational proteolysis generates diverse acidic and basic PRPs, with mutations affecting this process.
- Cysteine substitutions lead to disulfide-bonded homodimers and heterodimers with salivary peroxidase.
- Homologous and unequal crossing-over events result in protein size variants and fusion genes (e.g., PRB2/1), causing absence of specific PRPs.
- Null mutations, caused by single nucleotide changes, lead to the absence of certain PRPs.
Conclusions:
- Genetic polymorphisms in human salivary PRPs arise from multiple mechanisms including proteolysis, mutations, gene rearrangements, and crossing-over events.
- These variations contribute to the complexity of PRP expression and individual differences in saliva.
- Understanding PRP genetic diversity is crucial for studies on salivary function and composition.
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