Xanthomonas campestris expansin-like X domain is a structurally disordered beta-sheet macromolecule capable of synergistically enhancing enzymatic efficiency of cellulose hydrolysis.
OBJECTIVE
To biochemically characterize an expansin-like X protein domain from Xanthomonas campestris (XcEXLX1) and to study its synergy with cellulases in cellulose depolymerization.


RESULTS
The protein was purified using a combination of ion exchange and size exclusion chromatography rendering about 30 mg pure protein/l culture medium. Circular dichroism spectroscopy and small-angle X-ray scattering studies of XcEXLX1 reveal that it is a strongly disordered β-sheet protein. Its low resolution envelope fits nicely the crystallographic structure of the homologous protein EXLX1 from Bacillus subtillis. Furthermore, we demonstrate that XcEXLX1 shows a synergistic, pH-dependent effect when combined with a commercial enzymatic preparation (Accellerase 1500), enhancing its hydrolytic activity on a cellulosic substrate. The strongest effect was observed in acid pHs with an increase in sugar release of up to 36 %.


CONCLUSIONS
The synergistic effect arising from the action of the expansin-like protein was considerable in the presence of significantly larger amounts of the commercial enzymatic cocktail then previously observed (0.35 FPU of Accellerase 1500/g substrate).
Departamento de Física e Ciência Interdisciplinar, Instituto de Física de São Carlos, Universidade de São Paulo, Avenida Trabalhador 8 São Carlense 400 - Centro, São Carlos, SP, 13560-970, Brazil.
Atílio Tomazini
AT
Junior
Departamento de Física e Ciência Interdisciplinar, Instituto de Física de São Carlos, Universidade de São Paulo, Avenida Trabalhador 8 São Carlense 400 - Centro, São Carlos, SP, 13560-970, Brazil.
Luciano Graciani
LG
Dolce
Instituto de Biociências, Universidade Estadual Paulista, Distrito de Rubião Jr. s/n, Botucatu, SP, 18618970, Brazil.
Mario
M
de Oliveira Neto
Departamento de Física e Ciência Interdisciplinar, Instituto de Física de São Carlos, Universidade de São Paulo, Avenida Trabalhador 8 São Carlense 400 - Centro, São Carlos, SP, 13560-970, Brazil. ipolikarpov@ifsc.usp.br.
Igor
I
Polikarpov
D002482:Cellulose / Q000378:metabolism*; D002853:Chromatography, Liquid; D002942:Circular Dichroism; D003600:Cytosol / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D006867:Hydrolases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D006868:Hydrolysis; D011487:Protein Conformation; D053838:Scattering, Small Angle; D016959:Xanthomonas campestris / Q000201:enzymology*
D002482:Cellulose; D006867:Hydrolases
Accellerase; Biofuel; Cellulase; Cellulose depolymerization; Expansin synergism; Xanthomonas campestris