Local microdomain structure in the terminal extensions of betaA3- and betaB2-crystallins.
Mol Vis
; 4: 9, 1998 Jun 18.
Article
en En
| MEDLINE
| ID: mdl-9636238
ABSTRACT
PURPOSE:
Although the crystal structures of the core domains of bovine betaB2-crystallin have been determined and those of other betagamma-crystallins modeled, the positions of the N- and C-termini are not resolvable by X-ray crystallography. Here we model the possible structural organization of the terminal arms of mouse betaA3- and betaB2-crystallins and test this model against the results of partial proteolysis.METHODS:
The secondary structure of the terminal extensions was predicted by 3 different methods, one a nearest-neighbor method modified to use overlapping sequence tripeptides. Recombinant betaA3- and betaB2-crystallins were expressed using baculovirus vectors in S. frugiperda Sf9 cells. Crystallins were sequenced by the Edman degradation method.RESULTS:
The N-terminal extension of betaB2-crystallin includes a series of hydrophilic residues from Q-11 to Q-9 which have high propensity of a helical conformation. The N-terminal arm of betaA3-crystallin is also predicted to have two helical segments, from Q-24 to E-20 and M-13 to A-12. Partial characterization of the baculovirus extract showed a thiol protease inhibited by leupeptin and E-64. As predicted by the model, recombinant betaB2-crystallin subjected to partial proteolysis was cleaved adjacent to the helical domain, while the N-terminal cleavage site in recombinant betaA3-crystallin was within 1 residue of an interhelical junction. Our model also predicts the products of partial proteolytic degradation of betaB2- and betaA3-crystallins from human, rat, bovine and chicken lenses incubated with the protease m-calpain.CONCLUSIONS:
These results suggest the existence of local microdomain structures in the N- and C-terminal extensions of betaA3- and betaB2-crystallins, which appear to be more susceptible to proteolytic degradation in regions adjacent to these putative domains.
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Base de datos:
MEDLINE
Asunto principal:
Estructura Secundaria de Proteína
/
Cristalinas
/
Ratones
Tipo de estudio:
Prognostic_studies
Idioma:
En
Revista:
Mol Vis
Asunto de la revista:
BIOLOGIA MOLECULAR
/
OFTALMOLOGIA
Año:
1998
Tipo del documento:
Article