Mammalian mitochondrial ribosomal proteins are encoded by nuclear genes and help in protein synthesis within the mitochondrion. Mitochondrial ribosomes (mitoribosomes) consist of a small 28S subunit and a large 39S subunit. They have an estimated 75% protein to rRNA composition compared to prokaryotic ribosomes, where this ratio is reversed. Another difference between mammalian mitoribosomes and prokaryotic ribosomes is that the latter contain a 5S rRNA. Among different species, the proteins comprising the mitoribosome differ greatly in sequence, and sometimes in biochemical properties, which prevents easy recognition by sequence homology. This gene encodes a 39S subunit protein. Deletions in this gene may contribute to the etiology of velo-cardio-facial syndrome and DiGeorge syndrome.MRPL40 (Mitochondrial Ribosomal Protein L40) is a Protein Coding gene. Diseases associated with MRPL40 include Mrpl40-Related Disorder and Velocardiofacial Syndrome. Among its related pathways are Mitochondrial translation and Organelle biogenesis and maintenance. GO annotations related to this gene include poly(A) RNA binding.