IS THE BACTERIOPHAGE-LAMBDA LYSOZYME AN EVOLUTIONARY LINK OR A HYBRID BETWEEN THE C-TYPE AND V-TYPE LYSOZYMES - HOMOLOGY ANALYSIS AND DETECTION OF THE CATALYTIC AMINO-ACID-RESIDUES

The relationship between the bacteriophage lambda lysozyme (λL) and the C and V-type lysozymes has been investigated by sequence alignment, secondary structure prediction and pattern recognition methods. The alignment of the amino terminal part of λL with that of V-type lysozymes suggests that Glu19 is a residue essential for catalysis. Its mutation to Gln leads to a completely inactive enzyme. In the alignment of the sequence of λL with those of the C-type lysozymes a strongly homologous fragment of about 30 amino acid residues is detected. Taking into consideration this observation and the published structural alignments between C and V-type lysozymes, a repetition of the β-sheet motif in λL is proposed. The multiple alignment draws the attention to a possible catalytic role for Asp34 that would be positioned in the middle of the second strand of the β-sheet as in the C-type lysozymes. This role is confirmed by mutagenesis. The implications of these observations in terms of the evolutionary relationship between λL and the other lysozymes is discussed. © 1992.