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From Proteopedia
Crystal Structure of VHH R303 in complex with InlB-LRR
Structural highlights
FunctionINLB_LISMG Mediates the entry of L.monocytogenes into normally non-phagocytic mammalian host cells (Probable) (PubMed:11081636, PubMed:9282740). 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 PubMedListeria monocytogenes causes Listeriosis, a potentially fatal food borne disease. The condition is especially harmful to pregnant women. Listeria outbreaks can originate from diverse foods, highlighting the need for novel strategies to improve food safety. The first step in Listeria invasion is internalization of the bacteria, which is mediated by the interaction of the internalin family of virulence factors with host cell receptors. A crucial interaction for Listeria invasion of the placenta, and thus is a target for therapeutic intervention, is between Internalin B (InlB) and the receptor c-Met.. Single-domain antibodies (VHH, also called nanobodies, or sdAbs) from camel heavy-chain antibodies are a novel solution for preventing Listeria infections. The VHH R303, R330 and R326 all bind InlB with high affinity, however the molecular mechanism behind their mode of action was unknown. We demonstrate that despite a high degree of sequence and structural diversity, the VHH bind a single epitope on InlB. A combination of gentamicin protection assays and florescent microscopy establish that InlB specific VHH inhibit Listeria invasion of HeLa cells. A high resolution X-ray structure of VHH R303 in complex with InlB showed that the VHH binds at the c-Met interaction site on InlB, thereby acting as a competitive inhibitor preventing bacterial invasion. These results point to the potential of VHH as a novel class of therapeutics for the prevention of Listeriosis. Structural Basis of VHH mediated neutralization of the foodborne pathogen Listeria monocytogenes.,Toride King M, Huh I, Shenai A, Brooks TM, Brooks CL J Biol Chem. 2018 Jul 5. pii: RA118.003888. doi: 10.1074/jbc.RA118.003888. PMID:29976754[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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