Bacteriophage T4 encodes three ADP-ribosyltransferases, Alt, ModA, and ModB. These enzymes participate in the regulation of the T4 replication cycle by ADP-ribosylating a defined set of host proteins. In order to obtain a better understanding of the phage-host interactions and their consequences for regulating the T4 replication cycle, we studied cloning, overexpression, and characterization of purified ModA and ModB enzymes. Site-directed mutagenesis confirmed that amino acids, as deduced from secondary structure alignments, are indeed decisive for the activity of the enzymes, implying that the transfer reaction follows the Sn1-type reaction scheme proposed for this class of enzymes. In vitro transcription assays performed with Altand ModA-modified RNA polymerases demonstrated that the Alt-ribosylated polymerase enhances transcription from T4 early promoters on a T4 DNA template, whereas the transcriptional activity of ModA-modified polymerase, without the participation of T4-encoded auxiliary proteins for middle mode or late transcription, is reduced. The results presented here support the conclusion that ADP-ribosylation of RNA polymerase and of other host proteins allows initial phage-directed mRNA synthesis reactions to escape from host control. In contrast, subsequent modification of the other cellular target proteins limits transcription from phage early genes and participates in redirecting transcription to phage middle and late genes.Posttranslational ADP-ribosylation of proteins is catalyzed by ADP-ribosyltransferases (ADP-RTs), which have been identified in viral, bacterial, and eukaryotic systems. Transfer of the ADP-ribose moiety from the substrate NAD ϩ to a specific amino acid residue, frequently histidine or arginine within a target protein, modulates the activity of the acceptor. ADP-ribosylation changes the electrostatic potential of a target protein by introducing two phosphate groups and may affect protein-DNA as well as protein-protein interactions. ADP-RTs were initially discovered as the exotoxins of pathogenic bacteria. Therefore, most of our knowledge concerning these proteins has been gained by biochemical, genetic, and structural studies performed on bacterial toxins, such as those produced by Corynebacterium diphtheriae (15, 30), Bordetella pertussis (34), Vibrio cholerae (46), Pseudomonas aeruginosa (33), and Escherichia coli (45). New putative bacterial toxins were found to be encoded in the genomes of Streptococcus pyogenes and Salmonella enterica serovar Typhi (50).To date, the family of ADP-RTs comprises more than 40 enzymes, including bacterial exotoxins as well as a variety of other enzymes, such as the eukaryotic mono-and poly-ADPRTs, which include T-cell differentiation alloantigens like RT6 (9), poly-ADP-RTs (56), the dinitrogenase reductase regulation factor DraT (51,77), and enzymes encoded by T-even bacteriophages. The bacteriophage T4 gene products Alt (76 kDa), ModA (23 kDa), and ModB (24 kDa) appear to actively regulate gene expression during the transition from host t...

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KeywordsACE I/D polymorphism, angio-oedema, bradykinin, bradykinin B2 receptor polymorphism, serum ACE activity ---------------------------------------------------------------------- WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• Angiotensin-converting enzyme inhibitor (ACEi)-induced angio-oedema is an underestimated clinical life-threatening problem.• The incidence of this non-allergic, bradykinin-induced drug side-effect is 1 : 4000.• Although most ACEi-treated patients probably have an increased bradykinin plasma concentration, only 0.5% of them develop an angio-oedema and nothing is known about potential risk factors. WHAT THIS STUDY ADDS• In our attempt to elucidate the unpredictable character of ACEi-induced angio-oedema, we investigated bradykinin B2 receptor 2/3 and c.C181T polymorphisms as well as the ACE insertion/deletion polymorphism in combination with serum ACE activity in 65 patients.• ACE insertion/deletion and bradykinin B2 receptor polymorphisms are not involved in the development of ACEi-induced angio-oedema.• Further studies should be carried out to clarify whether a combination of these polymorphisms might be a risk factor for ACEi-induced angio-oedema. AIMSThe pathophysiology of angiotensin-converting enzyme inhibitor (ACEi)-induced angio-oedema remains unclear. We have investigated the impact of ACE insertion/deletion (I/D) polymorphism in combination with serum ACE activity as well as the bradykinin B2 receptor 2/3 and c.C181T polymorphisms. METHODSWe analysed the ACE I/D as well as bradykinin B2 (2/3 and C181T) receptor polymorphisms in 65 patients with documented episodes of ACEi-induced angio-oedema and 65 patients matched for age and sex being under ACEi treatment without history of angio-oedema. Furthermore, we determined serum ACE activity in 47 of the 65 angio-oedema patients 3 months after the angio-oedema attack and compared these values with 51 healthy individuals (control II). ; P = 0.9). RESULTS No risk association was identified between ACE CONCLUSIONSOur data suggest that polymorphism of ACE I/D and the bradykinin B2 receptor polymorphisms are not involved in the development of ACEi-induced angio-oedema when considered individually. Further studies should be carried out to clarify whether a combination of these polymorphisms might be a risk factor for ACEi-induced angio-oedema.

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