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4p29

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== Publication Abstract from PubMed ==
== Publication Abstract from PubMed ==
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Nontypeable Haemophilus influenzae is an obligate human parasite that often causes middle ear infections in children and exacerbates chronic obstructive pulmonary disorder, the fourth leading cause of death in the United States. There are no effective vaccines available for this strain. The lipoprotein YraM (gene HI1655) was identified as essential for the growth and viability of H. influenzae but its function is unknown. Sequence comparisons showed that YraM is a fusion of two protein modules. We grew crystals of the carboxyl-terminal module of YraM comprising residues 257-573 (YraM-C), phased the diffraction data by the multiwavelength anomalous diffraction technique, and refined the model to a crystallographic R-factor of 0.16 (R(free) = 0.19) with data to 1.35 A resolution. The two-domain structure of YraM-C adopts a fold similar to that observed for the open, unliganded forms of several periplasmic binding proteins (PBPs) involved in bacterial active transport. Sequence alignments of YraM homologues from other Gram-negative species showed that the most conserved residues of YraM-C cluster between the two domains in the location where other PBPs bind their cognate ligand. Modeling of YraM-C into a closed conformation similar to the leucine-bound form of the Leu/Ile/Val-binding protein (LIVBP) shows a putative binding pocket larger than the leucine-binding site in LIVBP. The pocket has both polar and nonpolar surfaces, with the latter located in the same area where a leucine side chain binds to LIVBP. We discuss possible biological functions of YraM considering its predicted location in the outer membrane, a novel place for such a binding protein. Proteins 2008. (c) 2008 Wiley-Liss, Inc.
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In many Gram-negative bacteria, the peptidoglycan synthase PBP1A requires the outer membrane lipoprotein LpoA for constructing a functional peptidoglycan required for bacterial viability. Previously, we have shown that the C-terminal domain of Haemophilus influenzae LpoA (HiLpoA) has a highly conserved, putative substrate-binding cleft between two alpha/beta lobes. Here, we report a 2.0-A-resolution crystal structure of the HiLpoA N-terminal domain. Two subdomains contain tetratricopeptide-like motifs that form a concave groove, but their relative orientation differs by ~45 degrees from that observed in an NMR structure of the Escherichia coli LpoA N domain. We also determined three 2.0-2.8-A-resolution crystal structures containing four independent full-length HiLpoA molecules. In contrast to an elongated model previously suggested for E. coli LpoA, each HiLpoA formed a U-shaped structure with a different C-domain orientation. This resulted from both N-domain twisting and rotation of the C domain (up to 30 degrees ) at the end of the relatively immobile interdomain linker. Moreover, a previously predicted hinge between the lobes of the LpoA C domain exhibited variations of up to 12 degrees . Small-angle X-ray scattering (SAXS) data revealed excellent agreement with a model calculated by normal mode analysis (NMA) from one of the full-length HiLpoA molecules, but even better agreement with an ensemble of this molecule and two of the partially extended NMA-predicted models. The different LpoA structures helped explain how an outer membrane-anchored LpoA can either withdraw from or extend toward the inner membrane-bound PBP1A through peptidoglycan gaps and hence regulate the synthesis of peptidoglycan necessary for bacterial viability.
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Structure of YraM, a protein essential for growth of Haemophilus influenzae.,Vijayalakshmi J, Akerley BJ, Saper MA Proteins. 2008 Apr 15;. PMID:18412262<ref>PMID:18412262</ref>
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Structural analyses of the Haemophilus influenzae peptidoglycan synthase activator LpoA suggest multiple conformations in solution.,Sathiyamoorthy K, Vijayalakshmi J, Tirupati B, Fan L, Saper MA J Biol Chem. 2017 Sep 8. pii: jbc.M117.804997. doi: 10.1074/jbc.M117.804997. PMID:28887305<ref>PMID:28887305</ref>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

Revision as of 10:07, 25 December 2019

Crystal structure of the LpoA N-terminal domain from Haemophilus influenzae

PDB ID 4p29

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