FIG 4.
Proposed model for fine-tuned vga(A) expression in response to antibiotics. (A) In the absence of antibiotic, transcription of vga(A) is prematurely terminated by the 5′ UTR secondary structure. (B) Ribosome stalled complex formed at uORF in the presence of lincosamide, streptogramin A, or pleuromutilin (LSAP) antibiotic to which a particular vga (A) variant does not confer resistance releases the transcription-permissive 5′ UTR secondary structure. Gene is transcribed; however, Vga(A) is not effectively translated at higher antibiotic concentrations, since Vga(A) cannot rescue the ribosome from inhibition. (C) In the presence of an LSAP antibiotic to which a particular Vga(A) variant confers resistance, ribosomes are protected, and Vga(A) is effectively translated proportionally to the amount of antibiotic. We speculate that direct modulation of the stalled ribosome complex by Vga(A) is part of regulation.