title: Ostrich crystallins. Structural characterization of delta-crystallin with enzymic activity.
abstract: Lens crystallins from the African ostrich (Struthio camelus) were isolated and characterized. Four crystallin fractions corresponding to alpha-, delta/beta- and beta-crystallins similar to those of duck crystallins were isolated, but epsilon-crystallin was found to be absent. The native molecular masses and subunit structures of the purified fractions were analysed by gel filtration. SDS/PAGE and isoelectric focusing, revealing various extents of heterogeneity in each orthologous crystallin class. An ion-exchange chromatographic method was used for the large-scale preparation of delta-crystallin suitable for structural and enzymic studies. It was unexpectedly found that the purified native delta-crystallin of ostrich lens possessed high argininosuccinate lyase activity, in contrast with chicken delta-crystallin. The c.d. spectra indicated a predominant beta-sheet structure in alpha- and beta-crystallins, and a significant contribution of alpha-helical structure in the delta-crystallin fraction. The estimate of secondary structures from c.d. spectroscopy for each crystallin class bears a resemblance to that of duck crystallins, except that ostrich delta-crystallin possesses much less helical content than duck delta-crystallin. Comparison of crystallin compositions and structures from aquatic and terrestrial birds revealed distinct differences.
authors.affiliation: Laboratory of Crystallin Research, National Taiwan University, Taipei, Republic of China.
authors.forename: S H
authors.initials: SH
authors.lastname: Chiou
authors.forename: C H
authors.initials: CH
authors.lastname: Lo
authors.forename: C Y
authors.initials: CY
authors.lastname: Chang
authors.forename: T
authors.initials: T
authors.lastname: Itoh
authors.forename: H
authors.initials: H
authors.lastname: Kaji
authors.forename: T
authors.initials: T
authors.lastname: Samejima
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001123:Argininosuccinate Lyase / Q000378:metabolism*; D001717:Birds; D002852:Chromatography, Ion Exchange; D003459:Crystallins / Q000737:chemistry* / Q000302:isolation & purification; D004591:Electrophoresis, Polyacrylamide Gel; D007525:Isoelectric Focusing; D007908:Lens, Crystalline / Q000737:chemistry* / Q000201:enzymology; D011487:Protein Conformation; D014508:Urea
chemical_list: D000596:Amino Acids; D003459:Crystallins; D014508:Urea; D001123:Argininosuccinate Lyase