Dynamic light scattering study of the two-domain structure of Humicola insolens endoglucanase V

Endoglucanase V (EG V) of HUmicola insolens is composed of a catalytic domain and of a cellulose-binding domain linked by a 33 amino acid long peptide rich in Ser, Thr and Pro residues. This work describes the dynamic behavior of the two-domain structure of EG V as revealed by quasi-elastic light scattering experiments. For both the full-length and the isolated catalytic domain, the autocorrelation function is essentially described by a single relaxation mode. The equivalent hydrodynamic radius of the catalytic domain was found to correspond precisely to the dimensions measured from the previously determined three-dimensional structure. The results obtained with the full-length protein allow a description of the two domain structure of EG V similar to that resulting from earlier studies using small angle X-ray scattering on cellulases from Trichoderma reesei. The hydrodynamic dimensions of the entire enzyme can be approximated as an ellipsoid with dimensions of 42 x 133.6 A.