Haemophilus influenzae Outer Membrane Protein P5 Is Associated with Inorganic Polyphosphate and Polyhydroxybutyrate

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...

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Bibliographic Details
Published in:Biophysical journal 2007-01, Vol.92 (2), p.588-593
Main Authors: Zakharian, E., Reusch, R.N.
Format: Article
Language:English
Subjects:
Bacterial Outer Membrane Proteins - chemistry
Bacterial proteins
Biophysics
Hydroxybutyrates - chemistry
Influenza
Inorganic Chemicals - chemistry
Lipid Bilayers - chemistry
Lipids
Membrane Fluidity
Membranes
Phospholipids - chemistry
Polyesters - chemistry
Polyphosphates - chemistry
Porosity
Supramolecular Assemblies
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Summary: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.
ISSN:0006-3495
1542-0086
DOI:10.1529/biophysj.106.095273