Identification and characterization of an autolysin gene, atlh, from Streptococcus downei

Curr Microbiol. 2009 May;58(5):432-7. doi: 10.1007/s00284-008-9336-0. Epub 2008 Dec 18.


An autolysin gene, atlh, was identified and sequenced from Streptococcus downei MFe28 using degenerate polymerase chain reaction (PCR) and the gene-walking method. Atlh protein encoded by atlh is composed of 879 amino acids, with a molecular weight of 95,902.26. Atlh possesses four 15-amino-acid residue repeats in the putative cell-wall-binding domain and has a catalytic domain in the C-terminus. The deduced amino acid sequence of atlh showed homology to S. mutans autolysin AtlA (68.4% similarity). Inactivation of atlh resulted in elongated chain formation compared to the parent strain. Recombinant proteins Atlh and its derivatives were constructed and analyzed by zymography. Zymographic analysis revealed that the Asp-771 residue of Atlh was essential for lytic activity and that lytic activity was not diminished by the deletion of repetitive regions in the putative cell-wall-binding domain of Atlh. Biofilm assay showed that the wild-type strain formed glucose- and sucrose-dependent biofilms, the atlh mutant diminished this ability. These results suggest that Atlh is associated with cell separation and biofilm formation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics*
  • Binding Sites
  • Biofilms / growth & development
  • Catalytic Domain
  • Cloning, Molecular
  • DNA, Bacterial / chemistry
  • DNA, Bacterial / genetics
  • Gene Deletion
  • Molecular Sequence Data
  • Molecular Weight
  • N-Acetylmuramoyl-L-alanine Amidase / chemistry
  • N-Acetylmuramoyl-L-alanine Amidase / genetics*
  • Repetitive Sequences, Amino Acid
  • Sequence Alignment
  • Sequence Analysis, DNA
  • Sequence Homology, Amino Acid
  • Streptococcus / genetics*


  • Bacterial Proteins
  • DNA, Bacterial
  • N-Acetylmuramoyl-L-alanine Amidase

Associated data

  • GENBANK/AB302222