S-adenosyl-L-methionine-dependent 2'-O-ribose methyltransferase that catalyzes the formation of 2'-O-methylguanosine at position 1580 (Gm1580) in the mitochondrial large subunit ribosomal RNA (mtLSU rRNA), a conserved modification in the peptidyl transferase domain of the mtLSU rRNA. a uridine in rRNA + S-adenosyl-L-methionine = a 2'-O-methyluridine in rRNA + H(+) + S-adenosyl-L-homocysteine Belongs to the class IV-like SAM-binding methyltransferase superfamily. RNA methyltransferase TrmH family.