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Smith B.P.,Program in Molecular and Cellular Biology | Smith B.P.,New York University | Roman C.A.J.,Program in Molecular and Cellular Biology | Roman C.A.J.,New York University
Molecular Immunology | Year: 2010

PreBCR signaling is critical for B cell development and normally depends on the association of a nascent, component Ig H chain with the surrogate L chain (SLC), which helps ensure that only B cells that synthesize structurally sound antibody can develop. How the invariant and λ-like SLC vets billions of unique V H domains for compatibility with polymorphic κ and λ L chains is unclear, because the SLC is composed of not only the Ig domains of VpreB and λ5, but also the unique regions (URs) that reside at what would be the L chain CDR3. We evaluated the contribution of the Ig and UR domains of λ5 to H chain screening by evaluating the preBCR-forming capability of λ5 mutants with a diverse panel of H chains. Using transformed mouse B cells, we demonstrate that the Ig domain of λ5 was sufficient and its UR dispensable for the rejection of V HQ52 and V H10 SLC-incompatible H chains. In contrast, the λ5 UR was necessary to discriminate between SLC-incompatible and -compatible V H81X H chains. Substituting the Ig domains of λ5 with equivalent κ sequences impaired the SLC's ability to escort all H chains to the surface. Two SLC-incompatible H chains were able to form surface BCRs with two κ L chains, indicating that the SLC's ability to predict the L chain compatibility of a H chain is not absolute. In sum, λ5 differentially relies on the λ-like Ig and UR to probe H chain structure to best accommodate diversity among H chains. © 2010 Elsevier Ltd. All rights reserved. Source


Romano F.B.,Program in Molecular and Cellular Biology | Tang Y.,Program in Molecular and Cellular Biology | Monopoli K.R.,Program in Molecular and Cellular Biology | Ross J.L.,Program in Molecular and Cellular Biology | And 2 more authors.
Journal of Biological Chemistry | Year: 2016

Atype 3 secretion system is used by many bacterial pathogens to inject proteins into eukaryotic cells. Pathogens insert a translocon complex into the target eukaryotic membrane by secreting two proteins known as translocators.Howthese translocators form a translocon in the lipid bilayer and why both proteins are required remains elusive. Pseudomonas aeruginosa translocators PopB and PopD insert pores into membranes forming homo- or hetero-complexes of undetermined stoichiometry. Single-molecule fluorescence photobleaching experiments revealed that PopD formed mostly hexameric structures in membranes, whereas PopB displayed a bi-modal distribution with 6 and 12 subunits peaks. However, individually the proteins are not functional for effector translocation.Wehave found that when added together, the translocators formed distinct heterocomplexes containing 8 PopB and 8 PopD molecules. Thus, the interaction between PopB and PopD guide the assembly of a unique hetero-oligomer in membranes. ©2016 by The American Society for Biochemistry and Molecular Biology, Inc. Source

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