title: Zebrafish alpha-crystallins: protein structure and chaperone-like activity compared to their mammalian orthologs.
abstract: OBJECTIVE
  The vertebrate small heat shock proteins alphaA- and alphaB-crystallin contribute to the transparency and refractive power of the lens and may also prevent the aggregation of non-native proteins that would otherwise lead to cataracts. We previously showed that zebrafish (Danio rerio) and human alphaB-crystallin have diverged far more in primary structure and expression pattern than the orthologous alphaA-crystallins. In this current study we further compare the structure and function of zebrafish and mammalian alpha-crystallins.
  
  
  METHODS
  Near UV CD spectroscopy was used to analyze the tertiary structure and thermal stability of recombinant zebrafish alpha-crystallins. The chaperone-like activities of zebrafish and human alpha-crystallins were compared by assaying their ability to prevent the chemically induced aggregation of several target proteins at temperatures between 25 degrees C and 40 degrees C.
  
  
  RESULTS
  Zebrafish and human alphaA-crystallin showed very similar tertiary structures, while the alphaB-crystallin orthologs showed differences related to the presence of additional aromatic amino acids in the zebrafish protein. The denaturation temperatures of zebrafish crystallins were lower than those of mammals. The chaperone-like activities of the two zebrafish alpha-crystallins were highly divergent, with alphaA-crystallin showing much greater activity than alphaB-crystallin.
  
  
  CONCLUSIONS
  alphaA-crystallin serves a similar physiological function in both zebrafish and mammals as a lens specific chaperone-like molecule. The reduced chaperone-like function of zebrafish alphaB-crystallin and its lack of extralenticular expression indicates that it plays a different physiological role from its mammalian ortholog. Future comparative studies of alpha-crystallin from closely related vertebrate species can help identify specific structural changes that lead to alterations in chaperone-like activity.
authors.affiliation: Department of Biology, Ashland University, Ashland, OH 44805, USA.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Dahlman
authors.forename: Kelli L
authors.initials: KL
authors.lastname: Margot
authors.forename: Linlin
authors.initials: L
authors.lastname: Ding
authors.forename: Joseph
authors.initials: J
authors.lastname: Horwitz
authors.forename: Mason
authors.initials: M
authors.lastname: Posner
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002417:Cattle; D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D018832:Molecular Chaperones / Q000378:metabolism*; D011489:Protein Denaturation; D017434:Protein Structure, Tertiary; D011817:Rabbits; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship; D015027:Zebrafish; D038202:alpha-Crystallin A Chain / Q000737:chemistry* / Q000378:metabolism; D038203:alpha-Crystallin B Chain / Q000737:chemistry* / Q000378:metabolism
chemical_list: D018832:Molecular Chaperones; D038202:alpha-Crystallin A Chain; D038203:alpha-Crystallin B Chain