Specifically methylates the N(7) position of guanine 1405 in 16S rRNA. Confers resistance to various aminoglycosides, including gentamicin and kanamycin. guanosine(1405) in 16S rRNA + S-adenosyl-L-methionine = N(7)-methylguanosine(1405) in 16S rRNA + S-adenosyl-L-homocysteine Protects Frankia sp., which is an antibiotic-producing bacterium, against self-intoxication. Belongs to the methyltransferase superfamily. Aminoglycoside resistance family.