- A sparsomycin-resistant mutant of Halobacterium salinarium lacks a modification at nucleotide U2603 in the peptidyl transferase centre of 23 S rRNA. Lázaro, E., Rodriguez-Fonseca, C., Porse, B., Ureña, D., Garrett, R.A., Ballesta, J.P. J. Mol. Biol. (1996)