Figure 10-1: Bacteriophage lysis genes. A. The lysis genes, with length in codons, of four lambdoid (l, P22, PS3, 21) and three non-lambdoid (P1, P2, T7) phages are shown: holin genes (vertical lines), endolysin genes (solid in gray or black), nested Rz (horizontally lined) - Rz1 (striped) genes (96, 111), and the antiholin genes lydB of P1 and lysA of P2 (left-slanted lines) (124). The Rz - Rz1 genes in P2 and T7 are called lysB - lysC and 18.5 - 18.7, respectively. Identical decoration schemes for any two boxes denotes that there is detectable sequence similarity. Among the endolysins, the enzymatic activities are: black = muramidase (lysozyme); light gray = transglycosylase; dark gray = amidase. White boxes are other phage genes not involved in lysis. In the case of the lambdoid holin genes with dual start motifs, the lengths of the holin and antiholin reading frames, in codons, is shown above each box. The names of the l lysis genes (S,R,Rz, and Rz1) are used for the lambdoid genes; the Salmonella phages P22 and PS3, the corresponding gene names would be 13,19,15 and Rz1, respectively. Note that in T7, the endolysin gene, 3.5, is located in an early gene cluster; its position in the lysis cassette is taken by an unrelated virion maturation gene. The positions of late gene promoters serving the lysis genes are indicated by arrows. Shown in the inset above the l lysis cassette is the 5' end of the S mRNA sequence, where two stem-loop structures control the partition of translational initiations between the start codons of the S107 and S105 reading frames. Nucleotide positions relative to the first base of codon 1 are shown in italics. Adapted from Young (120) and Johnson-Boaz et al. (65), with permission. B. S mutants. The parental S sequence and characterized mutations are shown in single letter code, with the starting residues of the S107 (Met1) and S105 (Met3) products underlined, predicted side-chain charge indicated above the sequence, and residues in the three TMDs enclosed in gray boxes. All alleles shown are missense except that x denotes a nonsense allele. Keys: upper case = early lysis alleles; lower case = unconditional lysis-defective alleles; lower case italic = delayed lysis alleles; strike-through = lysis-neutral alleles. Underlined and strike-through missense alleles are all single-cysteine substitutions derived from the C51S allele. Adapted from Young (120), with permission. (for better image quality, click here for tif image, which may be quite large; may also require screen refreshing plus special software to view; or view larger tif in separate window)

Figure 10-1, Figure 10-2, Figure 10-3, Figure 10-4, Figure 10-5, Figure 10-6, Figure 10-7, Figure 10-8, Figure 10-9, Figure 10-10

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