To determine if the mutation was predicted to disrupt protein function, we modeled human CLP1 using the structure of the partially crystallized yeast nucleotide-bound Clp1 (Noble et al., 2007). In yeast, the p.140ARG is substituted for a LYS at the cognate position, which is also a polar basic residue (p.149LYS). Structure shows that the yeast p.149LYS is involved in the formation of an inferred hydrogen bond with the highly conserved p.59GLU residue (Figure 2A). This polar contact is predicted to be maintained in human, but disrupted in the presence of the mutant p.140HIS residue, suggesting an alteration in protein structure or function. We found comparable CLP1 protein levels among all genotypes in primary fibroblast lysates derived from skin biopsy (Figure 2B), suggesting protein stability was unaltered in the presence of the mutation.
