4aw4
Engineered variant of Listeria monocytogenes InlB internalin domain with an additional leucine rich repeat inserted
Structural highlights
FunctionINLB_LISMG Mediates the entry of L.monocytogenes into normally non-phagocytic mammalian host cells (Probable) (PubMed:9282740, PubMed:11081636). Its host receptor is hepatocyte growth factor receptor (HGF receptor, a tyrosine kinase, MET) which is tyrosine-phosphorylated in response to InlB in human, green monkey, mouse and dog cell lines (PubMed:11081636, PubMed:15049825). Downstream adapter proteins GAB1 and CBL are phosphorylated in response to InlB, which also causes cell colony scattering (PubMed:11081636). InlB binding to mammalian cells is saturable and inhibited by EDTA; InlB-coated beads can be taken up by host cells (PubMed:10747014). Complement component 1 Q subcomponent-binding protein (gC1q-R, C1QBP) might act as an InlB receptor, leading to activation of PI3-kinase in green monkey cells (PubMed:10747014). Stimulation of Tyr-phosphorylation by InlB is antagonized by C1QBP, showing that potentiation of MET signaling via the GW domains is not mediated by C1QBP; the exact role of C1QBP remains to be determined (PubMed:15049825). Stimulation of Tyr-phosphorylation of MET by InlB is potentiated by the InlB GW domains and glycosaminoglycans such as heparin; exogenously added InlB, or hepatocyte growth factor (HGF) will also substitute for bacterial InlB, suggesting InlB promotes bacterial invasion by mimicking the hormone HGF (PubMed:15049825). May stimulate phosphatidylinositol 4,5-bisphosphate 3-kinase (PI3-kinase) in green monkey cells, has less effect in humans as PI3-kinase is constitutively and highly expressed in Caco cells (Probable). Binds heparin; C1QBP and heparin seem to bind to the GW domains (PubMed:12411480).[1] [2] [3] [4] [5] [6] [7] [8] Publication Abstract from PubMedThe physiological relevance of contacts in crystal lattices often remains elusive. This was also the case for the complex between the invasion protein internalin B (InlB) from Listeria monocytogenes and its host cell receptor, the human receptor tyrosine kinase (RTK) MET. InlB is aMET agonist and induces bacterialhost cell invasion.Activation of RTKs generally involves ligand-induced dimerization of the receptor ectodomain. The two currently available crystal structures of the InlB:MET complex show the same arrangement of InlB and MET in a 1:1 complex, but different dimeric 2:2 assemblies. Only one of these 2:2 assemblies is predicted to be stable by a computational procedure. This assembly is mainly stabilized by a contact between the Cap domain of InlB from one and the Sema domain of MET from another 1:1 complex.Here, we probe the physiological relevance of this interaction. We generatedvariants of the leucine-rich repeat (LRR) protein InlBby inserting an additional repeat between the first and the second LRR. This should allow formation of the 1:1 complex but disrupt the potential 2:2 complex involving the Cap-Sema contact due to steric distortions. A crystal structure of oneof the engineered proteins showed that it folded properly. Binding affinityto MET was comparable to that of wild-type InlB. The InlB variant induced MET phosphorylation and cell scatter like wild-type InlB.Theseresults suggestthat the Cap-Sema interaction is not physiologically relevant and support the previously proposed assembly, in which a 2:2 InlB-MET complex is built around a ligand dimer. Engineered variants of InlB with an additional leucine-rich repeat discriminate between physiologically relevant and packing contacts in crystal structures of the InlB:MET complex.,Niemann HH, Gherardi E, Bleymuller WM, Heinz DW Protein Sci. 2012 Aug 10. doi: 10.1002/pro.2142. PMID:22887347[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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