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Structural Insights into Cellulolytic and Chitinolytic Enzymes Revealing Crucial Residues of Insect b-N-acetyl-D-hexosaminidase.
- Source :
-
PLoS ONE . Dec2012, Vol. 7 Issue 12, p1-9. 9p. - Publication Year :
- 2012
-
Abstract
- The chemical similarity of cellulose and chitin supports the idea that their corresponding hydrolytic enzymes would bind b- 1,4-linked glucose residues in a similar manner. A structural and mutational analysis was performed for the plant cellulolytic enzyme BGlu1 from Oryza sativa and the insect chitinolytic enzyme OfHex1 from Ostrinia furnacalis. Although BGlu1 shows little amino-acid sequence or topological similarity with OfHex1, three residues (Trp490, Glu328, Val327 in OfHex1, and Trp358, Tyr131 and Ile179 in BGlu1) were identified as being conserved in the +1 sugar binding site. OfHex1 Glu328 together with Trp490 was confirmed to be necessary for substrate binding. The mutant E328A exhibited a 8-fold increment in Km for (GlcNAc)2 and a 42-fold increment in Ki for TMG-chitotriomycin. A crystal structure of E328A in complex with TMG-chitotriomycin was resolved at 2.5 Å , revealing the obvious conformational changes of the catalytic residues (Glu368 and Asp367) and the absence of the hydrogen bond between E328A and the C3-OH of the +1 sugar. V327G exhibited the same activity as the wild-type, but acquired the ability to efficiently hydrolyse β-1,2-linked GlcNAc in contrast to the wild-type. Thus, Glu328 and Val327 were identified as important for substrate-binding and as glycosidic-bond determinants. A structurebased sequence alignment confirmed the spatial conservation of these three residues in most plant cellulolytic, insect and bacterial chitinolytic enzymes. [ABSTRACT FROM AUTHOR]
- Subjects :
- *ENZYMES
*GENETIC mutation
*GENETICS
*HEXOSAMINIDASE
*PROTEINS
Subjects
Details
- Language :
- English
- ISSN :
- 19326203
- Volume :
- 7
- Issue :
- 12
- Database :
- Academic Search Index
- Journal :
- PLoS ONE
- Publication Type :
- Academic Journal
- Accession number :
- 84710523
- Full Text :
- https://doi.org/10.1371/journal.pone.0052225