Table 4 Distribution of alleles of the T4 DNA modification, restriction and antirestriction genes in T4-related phages⁽¹⁾

42

dCMP - hydroxymethylase

Hm-dCMP synthesis

All T-even type and JS98 type phages. Also phages RB69 and CC31, all 4 Acinetobacter phages (133, Acj9, Acj61 and Ac42) and the Aeromonas phages 44RR, 31 and 25.

56

dCTPase - dUTPase

Increases dCMP pool, decreases dCTP pool; provides dUMP for dTMP synthesis

All phages listed in Table 2, except the giant Aeromonas phages Aeh1 and 65 and the giant Vibrio phages KVP40 and nt-1.

α-gt

α glucosyl transferase

α glucosylation of Hm-dCMP DNA

T-even type phages only

β-gt

β glucosyl transferase

β-glucosylation of Hm-dCMP DNA

Phages T4 and CC31 only

βα-gt

β-1, 6-glucosyl-α- glucose transferase

β glucosylation of α-glucosylated Hm-dCMP DNA

All T-even type phages, except T4; also present in CC31

denA

Endonuclease II (Endo II)

Limited cleavage of unmodified (dCMP-containing) DNA

All T4 relatives, except the Acinetobacter phages and marine cyanophages listed in Table 2

denB

Endonuclease IV (Endo IV)

Extensive cleavage of unmodified (dCMP containing) DNA

Same distribution as gene 42

alc

Alc protein

Disallows transcription of unmodified (dCMP containing) DNA

Same distribution as gene 42

arn

Arn protein

Counters the restriction effects of the host McR (Rgl) system

All T-even type phages; and phage CC31 only.