title: Delta crystallins and their nucleic acids.
abstract: delta-Crystallin is a major structural protein of avian and reptilian lenses that is absent from the lenses of fish, amphibia and mammals. It appears to be a tetrameric protein with a native molecular weight near 200 000 (200K) and polypeptide molecular weight near 50K and 48K) (see Note added in proof). The alpha-crystallin polypeptides are extremely similar, associate in various combinations of four and are held together by hydrophobic interactions. Although principally cytoplasmic, delta-crystallin may associate with the cell membrane. delta-Crystallin differs from other lens crystallins in its alpha-helical content, native and subunit molecular weights, antigenicity, low wavelength of maximum fluorescence emission (315 nm) after excitation at 280 nm and amino acid composition (high in leucine; low in aromatic residues en no cysteine). Analyses of peptides, native and subunit molecular weights, and circular dichroism spectra indicate that the primary, secondary, tertiary and subunit structures of delta-crystallin have been generally conserved during evolution. There are at least two tandemly arranged delta-crystallin containing 13-15 introns in the chicken; a similar structure exists for a cloned delta-crystallin gene in the duck. Experiments with chicken show that delta-crystallin synthesis occurs principally in the embryo, especially during lens fiber cell differentiation. delta-Crystallin synthesis also takes place during lens fiber cell differentiation in culture. There is evidence for both transcriptional and post-transcriptional regulation of delta-crystallin synthesis. Current studies on the crystallographic and primary structures of delta-crystallin, on the structure, evolution and expression of the delta-crystallin genes, and on the translation of delta-crystallin mRNAs make this specialized lens protein an active area of investigation.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D001717:Birds; D002642:Chick Embryo; D003459:Crystallins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification; D003461:Crystallography; D004247:DNA / Q000032:analysis*; D004372:Ducks; D007526:Isoelectric Point; D007908:Lens, Crystalline / Q000032:analysis; D008970:Molecular Weight; D010455:Peptides / Q000032:analysis; D011188:Potassium / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis*; D012104:Reptiles; D012964:Sodium / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D003459:Crystallins; D010455:Peptides; D012333:RNA, Messenger; D004247:DNA; D012964:Sodium; D011188:Potassium