title: X-ray and neutron small-angle scattering analysis of the complex formed by the Met receptor and the Listeria monocytogenes invasion protein InlB.
abstract: The Listeria monocytogenes surface protein InlB binds to the extracellular domain of the human receptor tyrosine kinase Met, the product of the c-met proto-oncogene. InlB binding activates the Met receptor, leading to uptake of Listeria into normally nonphagocytic host cells. The N-terminal half of InlB (InlB(321)) is sufficient for Met binding and activation. The complex between this Met-binding domain of InlB and various constructs of the Met ectodomain was characterized by size exclusion chromatography and dynamic light scattering, and structural models were built using small-angle X-ray scattering and small-angle neutron scattering. Although most receptor tyrosine kinase ligands induce receptor dimerization, InlB(321) consistently binds the Met ectodomain with a 1:1 stoichiometry. A construct comprising the Sema and PSI domains of Met, although sufficient to bind the physiological Met ligand hepatocyte growth factor/scatter factor, does not form a complex with InlB(321) in solution, highlighting the importance of Met Ig domains for InlB binding. Small-angle X-ray scattering and small-angle neutron scattering measurements of ligand and receptor, both free and in complex, reveal an elongated shape for the receptor. The four Ig domains form a bent, rather than a fully extended, conformation, and InlB(321) binds to Sema and the first Ig domain of Met, in agreement with the recent crystal structure of a smaller Met fragment in complex with InlB(321). These results call into question whether receptor dimerization is the basic underlying event in InlB(321)-mediated Met activation and demonstrate differences in the mechanisms by which the physiological ligand hepatocyte growth factor/scatter factor and InlB(321) bind and activate the Met receptor.
authors.affiliation: Division of Structural Biology, Helmholtz Center for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany.
authors.forename: Hartmut H
authors.initials: HH
authors.lastname: Niemann
authors.forename: Maxim V
authors.initials: MV
authors.lastname: Petoukhov
authors.forename: Michael
authors.initials: M
authors.lastname: Härtlein
authors.forename: Martine
authors.initials: M
authors.lastname: Moulin
authors.forename: Ermanno
authors.initials: E
authors.lastname: Gherardi
authors.forename: Peter
authors.initials: P
authors.lastname: Timmins
authors.forename: Dirk W
authors.initials: DW
authors.lastname: Heinz
authors.forename: Dmitri I
authors.initials: DI
authors.lastname: Svergun
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D008089:Listeria monocytogenes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D009502:Neutrons; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D000090063:Proto-Oncogene Mas; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D053838:Scattering, Small Angle; D012996:Solutions; D014965:X-Rays
chemical_list: D001426:Bacterial Proteins; C000715470:MAS1 protein, human; D008565:Membrane Proteins; D000090063:Proto-Oncogene Mas; D012097:Repressor Proteins; D012996:Solutions; C095768:inlB protein, Listeria monocytogenes; C060486:methionine repressor protein, Bacteria