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The IS1 transposon has an amino acid triad similar to the catalytic site of the phage lambda Int integrases. Mutants of the His-200, Arg-203 and Tyr-231 amino acid residues were used to determine their function. All were necessary for transposase activity but different mutations caused different effects. A His-to-Gln mutation reduced transposase activity while a His-to-Leu mutation abolished activity.

Comparison of DNA-binding properties of the DA154 protein with six other FNR* proteins having amino acid substitutions indicates that there are at least two mechanisms by which FNR* substitution affects the activation of FNR. Mutants with substitution at position 154 exhibit DNA binding and apparently affect dimerization, allowing it to occur directly in the presence of oxygen. An additional factor may be required for other FNR* mutant proteins, which do not exhibit DNA binding. FNR is a global regulatory protein of Escherichia coli that controls gene expression in the absence of oxygen. The FNR* mutant proteins act when oxygen is present.

Plasmid, pCG79, obtained from Tn611 transposon insertion into pCG63, a temperature-sensitive plasmid isolated from an Escherichia coli mycobacterial shuttle vector with pAL5000 and pUC18 replicons, provided several insertional mutations in Mycobacterium smegmatis. This is the first time when straightforward transposition into a mycobacterium was utilized to build mycobacterial insertional mutant libraries. Preferential insertion regions were not identified.

An analysis of a partly-purified protein from an Escherichia coli cell extract that binds to the promoter site, and control transcription of the nrd operon, established it as the Escherichia coli factor for inversion stimulation. Two- to threefold-lower expression of an nrd-lac fusion is evident in mutants with deletion and site-directed mutations.

A study of the production of missense mutations influencing Asp-161 and Ser-163 in the S subunit of F1F0 ATP synthase, revealed that abolition of enzyme activity resulted from a delta-Asp-160 to Pro substitution, even though a majority of substitutions facilitated significant enzyme function. A structural breakdown modifying the enzyme complex was responsible for the lack of activity. The synthase function probably did not recognize any specific amino acids in the delta subunits.