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Evolution of immunoglobulin-like modules in chitinases: their structural flexibility and functional implications
A Perrakis1, C Ouzounis, K S Wilson
1Netherlands Cancer Institute, Department H2, Amsterdam, The Netherlands.
Folding & Design
|January 1, 1997
Summary
The immunoglobulin-like ChiN domain in Serratia marcescens chitinase A shares a similar fold but not sequence with fibronectin type III domains. These distinct evolutionary origins suggest ChiN domains interact with chitin during catalysis.
Area of Science:
- Enzymology
- Structural Biology
- Protein Evolution
Background:
- Chitinase A from Serratia marcescens is a glycosyl hydrolase with three domains.
- The N-terminal ChiN domain (amino acids 24-137) exhibits an immunoglobulin-like fold.
- This ChiN domain is structurally analogous to fibronectin type III (FnIII) domains found in other chitinases, yet lacks sequence similarity.
Purpose of the Study:
- To investigate the structural and evolutionary relationship between the ChiN domain and FnIII domains.
- To elucidate the functional role of the ChiN domain in chitinase activity.
Main Methods:
- Comparative structural analysis of ChiN and FnIII domains.
- Sequence searches and comparisons.
- Low-temperature structural determination of chitinase A.
Main Results:
- Structural comparisons confirmed the similar fold between ChiN and FnIII domains but revealed no sequence similarity.
- Sequence analyses indicated significant evolutionary divergence between ChiN and FnIII domains.
- The ChiN module demonstrated flexibility relative to the catalytic core of chitinase A.
Conclusions:
- The ChiN and FnIII domains likely evolved independently, despite their presence in otherwise homologous chitinases.
- The flexibility and structural characteristics of the ChiN domain suggest its involvement in chitin chain interaction during enzymatic catalysis.