The DNA base sequence of the pI promoter of the lambda-related phage 21 will be determined. We have already sequenced pI from phage 434. Phage 21 is of interest because, unlike 434, it has a different insertion site than lambda. However, its pI promoter responds to the cII protein. Mutations in the pI promoter of lambda will be identified and sequenced. The structural gene for biotin sulfoxide reductase (bisC) will be cloned on a multi-copy plasmid. This should provide us with sufficient bisC protein to obtain a pure product, as well as facilitating genetic analysis. Insertions of Mu Ap 1ac in bisC will be selected so that the regulation, if any, of bisC can be examined. We have found that this enzyme uses the same molybdenum cofactor (product of genes ch1A, ch1B, ch1E, ch1G) as nitrate reductase. The relation of those genes to bisC regulation will be tested. The birA gene, structural gene for the bifunctional protein holoenzyme-synthetase biotin-repressor, already cloned as a 2.1 kb segment, will be sequenced in wild type and mutant form.