Conformational plasticity links structural instability of NAA10F128I and NAA10F128L mutants to their catalytic deregulation

The acetylation of proteins' N-terminal amino groups by the N-acetyltransferase complexes plays a crucial role in modulating the spatial stability and functional activities of diverse human proteins. Mutations disrupting the stability and function of NAA10 result in X-linked rare genetic disorders. In this study, we conducted a global analysis of the impact of fifteen disease-associated missense mutations in <i>NAA10</i>. The analyses revealed that mutations in specific residues, such as Y43, V107, V111, and F128, predictably disrupted interactions essential for NAA10 stability, while most mutations (except R79C, A111W, Q129P, and N178K) expectedly led to structural destabilization. Mutations in many conserved residues within short linear motifs and post-translational modification sites were predicted to affect NAA10 functionality and regulation. All mutations were classified as pathogenic, with F128I and F128L identified as the most destabilizing mutations. The findings show that the F128L and F128I mutations employ different mechanisms for the loss of catalytic activities of NAA10^F128L and NAA10^F128I due to their structural instability. These two mutations induce distinct folding energy states that differentially modulate the structures of different regions of NAA10^F128L and NAA10^F128I. Specifically, the predicted instability caused by the F128I mutation results in decreased flexibility within the substrate-binding region, impairing the substrate peptide binding ability of NAA10^F128I. Conversely, F128L is predicted to reduce the flexibility of the region containing the acetyl-CoA binding residues in NAA10^F128L. Our study provides insights into the mechanism of catalytic inactivation of mutants of NAA10, particularly elucidating the mechanistic features of the structural and functional pathogenicity of the F128L and F128I mutations.