The structure of bacteriophage T7 lysozyme, a zinc amidase and an inhibitor of T7 RNA polymerase

Proc Natl Acad Sci U S A. 1994 Apr 26;91(9):4034-8. doi: 10.1073/pnas.91.9.4034.


The lysozyme of bacteriophage T7 is a bifunctional protein that cuts amide bonds in the bacterial cell wall and binds to and inhibits transcription by T7 RNA polymerase. The structure of a mutant T7 lysozyme has been determined by x-ray crystallography and refined at 2.2-A resolution. The protein folds into an alpha/beta-sheet structure that has a prominent cleft. A zinc atom is located in the cleft, bound directly to three amino acids and, through a water molecule, to a fourth. Zinc is required for amidase activity but not for inhibition of T7 RNA polymerase. Alignment of the zinc ligands of T7 lysozyme with those of carboxypeptidase A and thermolysin suggests structural similarity among the catalytic sites for the amidase and these zinc proteases. Mutational analysis identified presumed catalytic residues for amidase activity within the cleft and a surface that appears to be the site of binding to T7 RNA polymerase. Binding of T7 RNA polymerase inhibits amidase activity.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amidohydrolases / metabolism
  • Amidohydrolases / ultrastructure*
  • Amino Acid Sequence
  • Bacteriophage T7 / enzymology*
  • Binding Sites
  • Crystallography, X-Ray
  • DNA-Directed RNA Polymerases / antagonists & inhibitors*
  • Metalloproteins / ultrastructure
  • Molecular Sequence Data
  • Muramidase / chemistry
  • Muramidase / metabolism
  • Muramidase / ultrastructure*
  • Protein Structure, Tertiary
  • Structure-Activity Relationship
  • Viral Proteins
  • Zinc


  • Metalloproteins
  • Viral Proteins
  • bacteriophage T7 RNA polymerase
  • DNA-Directed RNA Polymerases
  • Muramidase
  • Amidohydrolases
  • Zinc

Associated data

  • GENBANK/V01146