title: Haemophilus influenzae outer membrane protein P5 is associated with inorganic polyphosphate and polyhydroxybutyrate.
abstract: Outer membrane protein P5 of nontypeable (acapsulate) Haemophilus influenzae (NTHi P5) forms large pores in planar lipid bilayers between symmetric solutions that unpredictably display a nonzero reversal potential. Moreover, NTHi P5 has a high theoretical isoelectric point, calculated as 9.58, which is not in agreement with the experimental isoelectric point, determined as 6.3-6.8, or with its preference for cations, disproportionately strong at one side. These anomalous results intimate that NTHi P5 is associated with a polyanion. Chemical and immunological analyses revealed the presence of inorganic polyphosphate (polyP), and the amphiphilic, solvating polyester, poly-(R)-3-hydroxybutyrate, frequently associated with polyP. A sharp reduction in cation selectivity was observed after addition of Saccharomyces cerevisiae exopolyphosphatase X to the bilayer, providing functional evidence for the involvement of polyP in selectivity. The results suggest that NTHi P5 associates with polyP and poly-(R)-3-hydroxybutyrate to create large, cation-selective pores in the outer membrane of H. influenzae.
authors.affiliation: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA.
authors.forename: E
authors.initials: E
authors.lastname: Zakharian
authors.forename: R N
authors.initials: RN
authors.lastname: Reusch
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D006885:Hydroxybutyrates / Q000737:chemistry*; D007287:Inorganic Chemicals / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D008560:Membrane Fluidity; D010743:Phospholipids / Q000737:chemistry*; D011091:Polyesters / Q000737:chemistry*; D011122:Polyphosphates / Q000737:chemistry*; D016062:Porosity; D000094122:Polyhydroxybutyrates
chemical_list: D001425:Bacterial Outer Membrane Proteins; D006885:Hydroxybutyrates; D007287:Inorganic Chemicals; D008051:Lipid Bilayers; D010743:Phospholipids; D011091:Polyesters; D011122:Polyphosphates; C082912:outer membrane protein P5, Haemophilus; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates