title: Evolutionary analysis of novel serine proteases in the venom gland transcriptome of Bitis gabonica rhinoceros.
abstract: BACKGROUND
  Serine proteases are major components of viper venom and target various stages of the blood coagulation system in victims and prey. A better understanding of the diversity of serine proteases and other enzymes present in snake venom will help to understand how the complexity of snake venom has evolved and will aid the development of novel therapeutics for treating snake bites.
  
  
  RESULTS
  Four serine protease-encoding genes from the venom gland transcriptome of Bitis gabonica rhinoceros were amplified and sequenced. Mass spectrometry suggests the four enzymes corresponding to these genes are present in the venom of B. g. rhinoceros. Two of the enzymes, rhinocerases 2 and 3 have substitutions to two of the serine protease catalytic triad residues and are thus unlikely to be catalytically active, though they may have evolved other toxic functions. The other two enzymes, rhinocerases 4 and 5, have classical serine protease catalytic triad residues and thus are likely to be catalytically active, however they have glycine rather than the more typical aspartic acid at the base of the primary specificity pocket (position 189). Based on a detailed analysis of these sequences we suggest that alternative splicing together with individual amino acid mutations may have been involved in their evolution. Changes within amino acid segments which were previously proposed to undergo accelerated change in venom serine proteases have also been observed.
  
  
  CONCLUSIONS
  Our study provides further insight into the diversity of serine protease isoforms present within snake venom and discusses their possible functions and how they may have evolved. These multiple serine protease isoforms with different substrate specificities may enhance the envenomation effects and help the snake to adapt to new habitats and diets. Our findings have potential for helping the future development of improved therapeutics for snake bites.
authors: Institute for Cardiovascular and Metabolic Research, University of Reading, Reading, United Kingdom. s.vaiyapuri@reading.ac.uk
authors: Sakthivel
authors: S
authors: Vaiyapuri
authors: Simon C
authors: SC
authors: Wagstaff
authors: Robert A
authors: RA
authors: Harrison
authors: Jonathan M
authors: JM
authors: Gibbins
authors: E Gail
authors: EG
authors: Hutchinson
mesh_terms: D000595:Amino Acid Sequence; D000825:Animal Structures / Q000201:enzymology*; D000818:Animals; D019143:Evolution, Molecular; D020869:Gene Expression Profiling; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014757:Viper Venoms / Q000201:enzymology* / Q000235:genetics*; D017819:Viperidae / Q000235:genetics*
chemical_list: D014757:Viper Venoms; D012697:Serine Endopeptidases