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Multiple crystal forms of endoglucanase CelD: signal peptide residues modulate lattice formation.
- Source :
-
Journal of molecular biology [J Mol Biol] 1995 Apr 28; Vol. 248 (2), pp. 225-32. - Publication Year :
- 1995
-
Abstract
- The crystal structure of Clostridium thermocellum endoglucanase CelD revealed an extended NH2-terminal segment (involving residues from the putative leader peptide) sticking out from the enzyme core to interact with a symmetry related molecule through an intermolecular salt bridge (Lys38-Asp201). Enzymatic digestion of CelD with various proteases emphasized the flexibility of the NH2-segment in solution. Proteolytic removal of Lys38 or the substitution of bridge-forming residues by site-directed mutagenesis promoted crystal packing arrangements that differ from that of wild type CelD. Crystals of wild-type CelD (a = 99.3 A c = 191.8 A) are trigonal, space group P3(1)21, with one molecule in the asymmetric unit (form A), whereas crystals of papain-treated CelD (a = 100.4 A, c = 248.7 A), of CelDK38M (a = 100.1 A, c = 248.4 A) and of papain-treated CelDD201A (a = 99.9 A, c = 250.0 A) are trigonal, space group P3(1)21, with two crystallographically independent molecules (form B), and crystals of chymotrypsin-treated CelD (a = 100.0 A, c = 254.3 A) and of CelDD201A (a = 99.8 A, c = 254.7 A) are hexagonal, space group P6(1)22, with one molecule in the asymmetric unit (form C). Only chymotrypsin-treated CelD (which preserves both Lys38 and Asp201) can grow in crystal form A upon macroseeding, indicating that formation of the intermolecular salt bridge is critical for stability of this crystal form. Flexible NH2- and COOH-terminal peptide extensions were found to influence crystal nucleation, but not crystal growth. The crystal structures of papain-treated CelD and chymotrypsin-treated CelD, determined at 3.5 A resolution by molecular replacement techniques, demonstrate that a small change in molecular orientation promoted by Lys38 account for the differences between crystal forms B and C.
- Subjects :
- Amino Acid Sequence
Bacterial Proteins metabolism
Cellulase metabolism
Crystallization
Crystallography, X-Ray
Endopeptidases metabolism
Hydrolysis
Models, Molecular
Molecular Sequence Data
Protein Sorting Signals metabolism
Bacterial Proteins chemistry
Cellulase chemistry
Clostridium enzymology
Protein Sorting Signals chemistry
Subjects
Details
- Language :
- English
- ISSN :
- 0022-2836
- Volume :
- 248
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- Journal of molecular biology
- Publication Type :
- Academic Journal
- Accession number :
- 7739036
- Full Text :
- https://doi.org/10.1016/s0022-2836(95)80045-x