Maldonado, Rafael, Herr, Alan J.
Efficiency of T4 Gene 60 Translational Bypassing
MALDONADO CARO, Rafael Diego; HERR, Alan J. “Efficiency of T4 Gene 60 Translational Bypassing”. Journal of Bacteriology. Vol. 180, No. 7 (Apr. 1998). ISSN 0021-9193, pp. 1822-1830
URI: http://hdl.handle.net/10045/3377
DOI: 
ISSN: 0021-9193
Abstract: 
Ribosomes translating bacteriophage T4 gene 60 mRNA bypass 50 noncoding nucleotides from a takeoff site
at codon 46 to a landing site just upstream of codon 47. A key signal for efficient bypassing is contained within
the nascent peptide synthesized prior to takeoff. Here we show that this signal is insensitive to the addition of
coding information at its N terminus. In addition, analysis of amino-terminal fusions, which allow detection of
all major products synthesized from the gene 60 mRNA, show that 50% of ribosomes bypass the coding gap
while the rest either terminate at a UAG stop codon immediately following codon 46 or fail to resume coding.
Bypassing efficiency estimates significantly lower than 50% were obtained with enzymatic reporter systems that
relied on comparing test constructs to constructs with a precise excision of the gap (gap deletion). Further
analysis showed that these estimates are distorted by differences between test and gap deletion functional
mRNA levels. An internal translation initiation site at Met12 of gene 60 (which eliminates part of the essential
nascent peptide) also distorts these estimates. Together, these results support an efficiency estimate of ~50%,
less than previously reported. This estimate suggests that bypassing efficiency is determined by the competition
between reading signals and release factors and gives new insight into the kinetics of bypassing signal action.
Keywords:Phage, Translation
American Society for Microbiology
info:eu-repo/semantics/article