FUNCTIONAL AND STRUCTURAL FEATURES OF THE HOLIN HOL PROTEIN OF THE LACTOBACILLUS-PLANTARUM PHAGE PHI-G1E - ANALYSIS IN ESCHERICHIA-COLI SYSTEM

Lactobacillus plantarum phage phi gle has two consecutive cell lysis g enes hol-lys (Oki et al., 1996b). In the present study, functional and structural properties of the hol protein (Hol) were characterized in Escherichia coli. Electron microscopic examinations showed that hol un der pine in E. coli XL1-Blue injured the inner membrane to yield empty ghost cells with the bulk of the cell wall undisturbed. Northern blot analysis indicated that hol-lys genes under pine were co-transcribed, although the amount of hol transcript was larger than that of lys, ce asing via an apparently rho-independent terminator just downstream of hol. However, deletion and/or fusion experiments suggested that: (1) t he N-terminal half of phi gle Hol composed of three putative transmemb rane domains may be responsible for interaction with membrane; (2) the N-terminal end (five amino acids) seems nonessential; and (3) the C-t erminal half containing charged amino acids appears to be involved in proper hol function. These results suggest that phi gle Hol is a membe r of the lambdoid holin family, but divergent in several properties fr om lambda holin. (C) 1997 Elsevier Science B.V.