Crustins are distinctive members of the WAP-containing protein superfamily: An improved classification approach

Dev Comp Immunol. 2017 Nov:76:9-17. doi: 10.1016/j.dci.2017.05.012. Epub 2017 May 13.

Abstract

Crustins are considered effector molecules of innate immunity in arthropods, and classification schemes have been proposed over the last 10 years. However, classification problems have emerged: for example, proteins that have been well identified as members of a particular category have also been classified as crustins. Therefore, the objective of this manuscript was to analyze and, based on solid arguments, improve the original proposed nomenclature to make crustins a distinctive group of antibacterial proteins. The presence of WAP or 4DSC domain has been considered a distinctive feature of crustins; however, several antibacterial proteins containing WAP domains have been detected in diverse taxonomic groups (including mammals). Here, we present evidence supporting the idea that the Cys-rich region and the 4DSC domain can be considered a signature of crustins and, together with some distance arrangements occurring within this 12-Cys region, yield enough information for the classification of these proteins. Herein, the core characteristics to be considered for classification purposes are the length of the Gly-rich region and the repetitive tetrapeptides occurring within this region; these characteristics are then hierarchically followed by the F and A distances located within the 4DSC domain. Finally, the proposed system considers the crustin signature as the common structure in all members, which is a differentiator from other proteins containing WAP domains, separating crustins as a well-distinguished member of the superfamily of WAP-domain containing proteins.

Keywords: 4DSC domain; Antibacterial; Classification; Crustacean; WAP domain.

Publication types

  • Review

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antimicrobial Cationic Peptides / genetics*
  • Arthropod Proteins / genetics*
  • Arthropods / genetics
  • Immunity, Innate / genetics
  • Sequence Alignment

Substances

  • Antimicrobial Cationic Peptides
  • Arthropod Proteins