Evidence for a third structural class of beta-1,3-glucanase in tobacco

Plant Mol Biol. 1990 Dec;15(6):797-808. doi: 10.1007/BF00039420.


Glucan endo-1,3-beta-glucosidases (beta-1,3-glucanases) have been implicated in several developmental processes and they may also play a direct role in the plant's defense against fungal pathogens. In an effort to characterize the glucanase gene family, complementary DNA clones encoding an acidic form of beta-1,3-glucanase have been isolated from tobacco. The cDNA was expressed in E. coli and shown to encode a beta-1,3-glucanase activity. The protein sequence encoded by the cDNA was found to match the partial protein sequence of PR-35, a previously characterized beta-1,3-glucanase. The protein encoded by the cDNA was purified from the extracellular fluid of TMV-infected tobacco leaves and found by immunological methods to correspond to glucanase PR-Q'. From a detailed analysis of the cDNA it is clear that this glucanase represents a third structural class of enzyme which differs substantially from both the basic, vacuolar glucanase and the acidic, extracellular forms (PR-2, PR-N and PR-O). It has previously been demonstrated that the basic form of beta-1,3-glucanase is synthesized as a pre-pro-enzyme and upon maturation the 21 amino acid signal peptide and a 22 amino acid carboxy-terminal peptide are removed. This processing event has been proposed to be involved with the vacuolar localization of the enzyme. By comparing the deduced protein structure of PR-Q' to that of the basic form it is evident that this extracellular enzyme is missing the carboxy-terminal 22 amino acids. The role of a conserved phenylalanine-glycine dipeptide in the processing of glucanases and other pathogenesis-related proteins from tobacco is discussed.

Publication types

  • Comparative Study

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cellulase / biosynthesis
  • Cellulase / chemistry
  • Cellulase / genetics*
  • Chitinases / genetics
  • DNA / genetics
  • Extracellular Space / enzymology*
  • Genes, Plant*
  • Molecular Sequence Data
  • Molecular Structure
  • Mosaic Viruses / physiology
  • Plant Proteins / biosynthesis
  • Plant Proteins / genetics*
  • Plants, Toxic*
  • Protein Processing, Post-Translational
  • Recombinant Proteins / biosynthesis
  • Sequence Homology, Nucleic Acid
  • Tobacco / enzymology
  • Tobacco / genetics*


  • Plant Proteins
  • Recombinant Proteins
  • pathogenesis-related proteins, plant
  • DNA
  • Chitinases
  • Cellulase

Associated data

  • GENBANK/X54456