| Abstract
| - A molecular envelope of the β-mannosidase from Trichoderma reesei has been obtained bycombined use of solution small-angle X-ray scattering (SAXS) and protein crystallography. Crystallographicdata at 4 Å resolution have been used to enhance informational content of the SAXS data and to obtainan independent, more detailed protein shape. The phased molecular replacement technique using a lowresolution SAXS model, building, and refinement of a free atom model has been employed successfully.The SAXS and crystallographic free atom models exhibit a similar globular form and were used to assessavailable crystallographic models of glycosyl hydrolases. The structure of the β-galactosidase, a memberof a family 2, clan GHA glycosyl hydrolases, shows an excellent fit to the experimental molecular envelopeand distance distribution function of the β-mannosidase, indicating gross similarities in their three-dimensional structures. The secondary structure of β-mannosidase quantified by circular dichroismmeasurements is in a good agreement with that of β-galactosidase. We show that a comparison of distancedistribution functions in combination with 1D and 2D sequence alignment techniques was able to restrictthe number of possible structurally homologous proteins. The method could be applied as a general methodin structural genomics and related fields once protein solution scattering data are available.
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