The function of ENSG00000171861 (MRM3, mitochondrial rRNA methyltransferase 3) is as follows. S-adenosyl-L-methionine-dependent 2'-O-ribose methyltransferase that catalyzes the formation of 2'-O-methylguanosine at position 1370 (Gm1370) in the 16S mitochondrial large subunit ribosomal RNA (mtLSU rRNA), a conserved modification in the peptidyl transferase domain of the mtLSU rRNA (PubMed:24036117, PubMed:25009282, PubMed:25074936, PubMed:35177605). Also required for formation of 2'-O- methyluridine at position 1369 (Um1369) mediated by MRM2 (PubMed:35177605). {ECO:0000269|PubMed:24036117, ECO:0000269|PubMed:25009282, ECO:0000269|PubMed:25074936, ECO:0000269|PubMed:35177605}.