Small ribosomal subunit protein uS9m

Small ribosomal subunit protein uS9m (MRPS9) is a mitochondrial ribosomal protein component encoded by the MRPS9 gene (UniProt: P82933). It functions as part of the 28S mitochondrial ribosomal subunit, essential for mitochondrial protein synthesis. The protein is 396 amino acids in length with a molecular mass of approximately 45.8 kDa.

MRPS9 is a component of mitochondrial translation machinery, with expression detected across tissues that maintain high metabolic demand. UniProt records no specific disease associations in curated evidence. However, curation within the Chaparral Knowledge Platform identifies this protein as relevant to Alzheimer's Disease pathology.

In human post-mortem Alzheimer's Disease brain tissue compared to age-matched controls (TMT-labeled proteomics across four subcellular fractions: P2, P3, S2, S3), MRPS9 shows significant downregulation with a mean log2 fold-change of −0.692 (Chaparral AD proteomics). This reduction in mitochondrial ribosomal protein abundance may reflect compromised mitochondrial protein synthesis capacity in AD-affected brain regions, consistent with documented mitochondrial dysfunction in Alzheimer's pathology.