Biophysical characterization of MMACHC mutants: towards targeted therapies for the vitamin B12 metabolism disorder cblC

Abstract

Disorders of Vitamin B12 metabolism, particularly methylmalonic academia with homocystinuria cblC type, caused by mutations in the MMACHC gene, present significant challenges in precision medicine due to their heterogeneous clinical manifestations. This heterogeneity arises from a broad mutational spectrum in the affected gene, leading to the production of misfolded, truncated, or aberrant proteins due to potential frameshift mutations. The expression levels of these proteins are highly variable, with the possible occurrence of Nonsense-Mediated RNA Decay in some cases [1]. Our research focuses on characterizing the molecular mechanisms underlying protein MMACHC dysfunctions caused by some common mutations identified in cblC patients. These include the missense mutation c.482G>A (p.R161Q) and the nonsense mutation c.394C>T (p.R132X) [2,3]. By using a battery of biophysical techniques—including spectroscopy, microcalorimetry, hydrodynamics, and Light and Small-Angle X-ray Scattering—we investigated how the stability, structural and binding properties, as well as the functional dimerization propensity of MMACHC, are influenced by these specific mutations.4 Understanding the chemical and physical features of MMACHC affected by specific mutations is a crucial step toward designing potential therapeutic interventions within a precision medicine framework. Notably, we found that small molecules such as chemical chaperones or Translational Readthrough-Inducing Drugs (TRIDs) could be explored as pharmacological treatments, provided that molecular insights are correlated with the expression levels of the mutated proteins. These findings enhance our understanding of MMACHC-related pathophysiology and reinforce the critical role of prescriptomics in bridging molecular research with clinical applications