T4-induced alpha- and beta-glucosyltransferase: cloning of the genes and a comparison of their products based on sequencing data.

Bacteriophage T4 alpha- and beta-glucosyltransferases link glucosyl units to the 5-HMdC residues of its DNA. The monoglucosyl group in alpha-linkage predominates over the one in beta linkage. Having recently reported on the nucleotide sequence of gene alpha gt (1) we now determined the nucleotide sequence of gene beta gt. The genes were each cloned on a high expression vector under the control of the lambda pL promoter. After thermo-induction the proteins were isolated and purified to homogeneity. To verify that the translational starting sites and the proposed reading frames are effective in vivo the sequence of the first 31 amino acid residues from gp alpha gt and the first 30 amino acid residues from gp beta gt were determined by Edman degradation. The primary structures of the two proteins seem to have only limited structural similarities. The results are discussed comparing secondary structure predictions and homologies with other proteins from the protein sequence database of the Protein Identification Resource.