title: Outer-membrane lipoprotein LpoB spans the periplasm to stimulate the peptidoglycan synthase PBP1B.
abstract: Bacteria surround their cytoplasmic membrane with an essential, stress-bearing peptidoglycan (PG) layer. Growing and dividing cells expand their PG layer by using membrane-anchored PG synthases, which are guided by dynamic cytoskeletal elements. In Escherichia coli, growth of the mainly single-layered PG is also regulated by outer membrane-anchored lipoproteins. The lipoprotein LpoB is required for the activation of penicillin-binding protein (PBP) 1B, which is a major, bifunctional PG synthase with glycan chain polymerizing (glycosyltransferase) and peptide cross-linking (transpeptidase) activities. Here, we report the structure of LpoB, determined by NMR spectroscopy, showing an N-terminal, 54-aa-long flexible stretch followed by a globular domain with similarity to the N-terminal domain of the prevalent periplasmic protein TolB. We have identified the interaction interface between the globular domain of LpoB and the noncatalytic UvrB domain 2 homolog domain of PBP1B and modeled the complex. Amino acid exchanges within this interface weaken the PBP1B-LpoB interaction, decrease the PBP1B stimulation in vitro, and impair its function in vivo. On the contrary, the N-terminal flexible stretch of LpoB is required to stimulate PBP1B in vivo, but is dispensable in vitro. This supports a model in which LpoB spans the periplasm to interact with PBP1B and stimulate PG synthesis.
authors.affiliation: Centre for Bacterial Cell Biology.
authors.forename: Alexander J F
authors.initials: AJ
authors.lastname: Egan
authors.affiliation: Institut de Biologie Structurale, Université Grenoble Alpes, F-38027 Grenoble, France;Institut de Biologie Structurale, Direction des Sciences du Vivant, Commissariat à l'Energie Atomique, F-38027 Grenoble, France;Institut de Biologie Structurale, Centre National de la Recherche Scientifique, F-38027 Grenoble, France;
authors.forename: Nicolas L
authors.initials: NL
authors.lastname: Jean
authors.affiliation: European Molecular Biology Laboratory, Genome Biology Unit, 69117 Heidelberg, Germany; and.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Koumoutsi
authors.affiliation: Institut de Biologie Structurale, Université Grenoble Alpes, F-38027 Grenoble, France;Institut de Biologie Structurale, Direction des Sciences du Vivant, Commissariat à l'Energie Atomique, F-38027 Grenoble, France;Institut de Biologie Structurale, Centre National de la Recherche Scientifique, F-38027 Grenoble, France;
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Bougault
authors.affiliation: Centre for Bacterial Cell Biology.
authors.forename: Jacob
authors.initials: J
authors.lastname: Biboy
authors.affiliation: Centre for Bacterial Cell Biology.
authors.forename: Jad
authors.initials: J
authors.lastname: Sassine
authors.affiliation: Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4AX, United Kingdom;
authors.forename: Alexandra S
authors.initials: AS
authors.lastname: Solovyova
authors.affiliation: Department of Biochemistry of Membranes, Bijvoet Center for Biomolecular Research, University of Utrecht, 3584 CH, Utrecht, The Netherlands.
authors.forename: Eefjan
authors.initials: E
authors.lastname: Breukink
authors.affiliation: European Molecular Biology Laboratory, Genome Biology Unit, 69117 Heidelberg, Germany; and typas@embl.de w.vollmer@ncl.ac.uk jean-pierre.simorre@ibs.fr.
authors.forename: Athanasios
authors.initials: A
authors.lastname: Typas
authors.affiliation: Centre for Bacterial Cell Biology, typas@embl.de w.vollmer@ncl.ac.uk jean-pierre.simorre@ibs.fr.
authors.forename: Waldemar
authors.initials: W
authors.lastname: Vollmer
authors.affiliation: Institut de Biologie Structurale, Université Grenoble Alpes, F-38027 Grenoble, France;Institut de Biologie Structurale, Direction des Sciences du Vivant, Commissariat à l'Energie Atomique, F-38027 Grenoble, France;Institut de Biologie Structurale, Centre National de la Recherche Scientifique, F-38027 Grenoble, France; typas@embl.de w.vollmer@ncl.ac.uk jean-pierre.simorre@ibs.fr.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Simorre
mesh_terms: D001055:Apolipoproteins B / Q000737:chemistry / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D046915:Penicillin-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D010457:Peptidoglycan / Q000096:biosynthesis; D046928:Peptidoglycan Glycosyltransferase / Q000737:chemistry / Q000378:metabolism*; D019897:Periplasm / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D017434:Protein Structure, Tertiary; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001055:Apolipoproteins B; D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D046915:Penicillin-Binding Proteins; D010457:Peptidoglycan; D046928:Peptidoglycan Glycosyltransferase; C478681:penicillin-binding protein 1B, E coli; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase