Comparative Analysis of Individual Domains of Hoc Proteins in Subfamily Teequatrovirinae Bacteriophages

This paper presents the results of a comparative study of the immunoglobulin-like domains in the genomes of phages related to bacteriophage T4. It is proposed to use Hoc proteins for the classification of subfamily Teequatrovirinae phages. A phylogenetic analysis was conducted for Hoc protein domains from 31 bacteriophages of the subfamily . It is shown that the number of domains in proteins of various bacteriophages of the subfamily varies from one to five. According to these findings the bacteriophages can be divided into six sub-groups. The phylogenetic tree of the protein domains of T4-related bacteriophages forms three main branches. Obligatory presence of the C-terminal domain in all proteins points to its functional and structural importance for the formation of the protein and its ability to attach to the phage capsid. A hypothetical scheme is formulated of the evolutionary origin of repeated amino acid sequences in Hoc proteins.