Identification and characterization of the metal ion-dependent L-alanoyl-D-glutamate peptidase encoded by bacteriophage T5.

Although bacteriophage T5 is known to have lytic proteins for cell wall hydrolysis and phage progeny escape, their activities are still unknown. This is the first report on the cloning, expression and biochemical characterization of a bacteriophage T5 lytic hydrolase. The endolysin-encoding lys gene of virulent coliphage T5 was cloned in Escherichia coli cells, and an electrophoretically homogeneous product of this gene was obtained with a high yield (78% of total activity). The protein purified was shown to be an L-alanoyl-D-glutamate peptidase. The enzyme demonstrated maximal activity in diluted buffers (25-50 mM) at pH 8.5. The enzyme was strongly inhibited by EDTA and BAPTA, and fully reactivated by calcium/manganese chlorides. It was found that, along with E. coli peptidoglycan, peptidase of bacteriophage T5 can lyse peptidoglycans of other Gram-negative microorganisms (Pectobacterium carotovorum, Pseudomonas putida, Proteus vulgaris, and Proteus mirabilis). This endolysin is the first example of an L-alanoyl-D-glutamate peptidase in a virulent phage infecting Gram-negative bacteria. There are, however, a great many sequences in databases that are highly similar to that of bacteriophage T5 hydrolase, indicating a wide distribution of endolytic L-alanoyl-D-glutamate peptidases. The article discusses how an enzyme with such substrate specificity could be fixed in the process of evolution.

Identification, cloning, and expression of bacteriophage T5 dnk gene encoding a broad specificity deoxyribonucleoside monophosphate kinase (EC 2.7.4.13).

The nucleotide sequence corresponding to 13-19.5% of the bacteriophage T5 genome in early region C was determined (GenBank AY 140897). One of the five major single-stranded interruptions (nicks) of bacteriophage T5 DNA was identified at 18.5%. The sequenced region was annotated and the putative functions of some open reading frames were proposed by comparison with databases. The dnk gene, encoding a deoxyribonucleoside monophosphate kinase, was identified using a previously defined N-terminal amino acid sequence. The gene was cloned and expressed in Escherichia coli, the enzyme was purified to homogeneity with high yield using two alternative methods, and the recombinant deoxyribonucleoside monophosphate kinase was found to have the same activity and specificity as the native enzyme.

Purification and characterization of the deoxynucleoside monophosphate kinase of bacteriophage T5.

Deoxynucleoside monophosphate kinase (dNMP kinase) of bacteriophage T5 (EC 2.7.4.13) was purified to apparent homogeneity from phage-infected Escherichia coli cells. Electrophoresis in sodium dodecyl sulfate-polyacrylamide gel showed that the enzyme has a molecular mass of about 29 kDa. The molecular mass of dNMP kinase estimated by analytical equilibrium ultracentrifugation turned out to be 29.14 +/- 3.03 kDa. These data suggest that the enzyme exists in solution as a monomer. The isoelectric point of dNMP kinase was found to be 4.2. The N-terminal amino acid sequence, comprising 21 amino acids, was determined to be VLVGLHGEAGSGKDGVAKLII. A comparison of this amino acid sequence and those of known enzymes with a similar function suggests the presence of a nucleotide-binding site in the sequenced region.