The invention provides vectors and methods designed for screening large random DNA fragment libraries for the presence of open reading frames that are free of both internal ribosome binding sites (IRBS) and stop codons. The invention overcomes the principal limitation of known ORF-selector systems, namely the potential for ORF-induced folding interference of the downstream fused reporter, by not fusing the reporter to the ORF, but rather by providing a mechanism for coupled translation of an unfused downstream reporter.
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with government support under Contract No. W-7405-ENG-36 awarded by the United States Department of Energy to The Regents of The University of California. The government has certain rights in this invention.