PAN-modular structure of microneme protein SML-2 from the parasite Sarcocystis muris at 1.95 Å resolution and its complex with 1-thio-β-D-galactose

Item Type:	Article
Title:	PAN-modular structure of microneme protein SML-2 from the parasite Sarcocystis muris at 1.95 Å resolution and its complex with 1-thio-β-D-galactose
Creators Name:	Mueller, J.J. and Weiss, M.S. and Heinemann, U.
Abstract:	The microneme protein SML-2 is a member of a small family of galactose-specific lectins that play a role during host-cell invasion by the apicomplexan parasite Sarcocystis muris. The structures of apo SML-2 and the 1-thio-{beta}-D-galactose-SML-2 complex were determined at 1.95 and 2.1 Å resolution, respectively, by sulfur-SAD phasing. Highly elongated dimers are formed by PAN-domain tandems in the protomer, bearing the galactose-binding cavities at the distal apple-like domains. The detailed structure of the binding site in SML-2 explains the high specificity of galactose-endgroup binding and the broader specificity of the related Toxoplasma gondii protein TgMIC4 towards galactose and glucose. A large buried surface of highly hydrophobic character and 24 intersubunit hydrogen bonds stabilize the dimers and half of the 12 disulfides per dimer are shielded from the solvent by the polypeptide chain, thereby enhancing the resistance of the parasite protein towards unfolding and proteolysis that allows it to survive within the intestinal tracts of the intermediate and final hosts.
Keywords:	Sarcocystis Muris, Parasites, Lectins, Apicomplexans, Microneme, Apple Domain, PAN_AP
Source:	Acta Crystallographica Section D
ISSN:	0907-4449
Publisher:	International Union of Crystallography
Volume:	67
Number:	Pt 11
Page Range:	936-944
Date:	November 2011
Official Publication:	https://doi.org/10.1107/S0907444911037796
PubMed:	View item in PubMed

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