Compensatory epistasis explored by molecular dynamics simulations

Area of Science:

• Biochemistry
• Genetics
• Molecular Biology

Background:

• Human pathogenic variants are sometimes found as wild type in other mammalian species.
• Compensatory epistasis is the proposed mechanism, but specific interacting residues are rarely identified.
• This study investigates compensated variants in X-linked human proteins.

Purpose of the Study:

• To identify candidate compensated variants in five human X-chromosomal proteins.
• To provide strong evidence for a compensated/compensatory amino acid pair in coagulation Factor IX (FIX).
• To elucidate the molecular interactions underlying this compensation using simulations.

Main Methods:

• Analysis of five human X-chromosomal proteins (FIX, GLA, HPRT1, NDP, OTC).
• Identification of candidate compensated variants across mammalian species.
• Molecular dynamics simulations to investigate residue interactions.

Main Results:

• Several candidate compensated variants were identified.
• Strong evidence found for a compensated/compensatory pair at residues 270 and 271 in coagulation FIXa.
• Molecular dynamics simulations revealed that Pro271 mitigates steric hindrance caused by the Glu270Lys substitution (hemophilia B).

Conclusions:

• A compensated/compensatory amino acid pair (residues 270 and 271) in coagulation FIXa was identified and validated.
• This pair plays a crucial role in mitigating the pathogenic effects of specific mutations.
• The findings enhance understanding of molecular mechanisms underlying variant compensation in mammals.