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Expression, purification, crystallization and preliminary crystallographic analysis of PilA from the nontypeable Haemophilus influenzae type IV pilus.

ABSTRACT: The type IV pili of nontypeable Haemophilus influenzae (NTHi) are involved in twitching motility, adherence, competence and biofilm formation. They are potential virulence factors for this important human pathogen and are thus considered to be vaccine targets. To characterize these pili, an attempt to solve the atomic structure of the major pilin subunit PilA was initiated. A 1.73 Å resolution X-ray diffraction data set was collected from native N-terminally truncated PilA (?N-PilA). Data processing indicated a hexagonal crystal system, which was determined to belong to space group P6(1) or P6(5) based on the systematic absences and near-perfect twinning of the crystal. The unit-cell parameters were a = b = 68.08, c = 197.03 Å with four molecules in the asymmetric unit, giving a solvent content of 50%. Attempts to solve the ?N-PilA structure by molecular replacement with existing type IV pilin and type II secretion pseudopilin structures are in progress.

SUBMITTER: Kolappan S

PROVIDER: S-EPMC3310531 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

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Expression, purification, crystallization and preliminary crystallographic analysis of PilA from the nontypeable Haemophilus influenzae type IV pilus.

Kolappan Subramaniapillai S Tracy Erin N EN Bakaletz Lauren O LO Munson Robert S RS Craig Lisa L

Acta crystallographica. Section F, Structural biology and crystallization communications 20120222 Pt 3

The type IV pili of nontypeable Haemophilus influenzae (NTHi) are involved in twitching motility, adherence, competence and biofilm formation. They are potential virulence factors for this important human pathogen and are thus considered to be vaccine targets. To characterize these pili, an attempt to solve the atomic structure of the major pilin subunit PilA was initiated. A 1.73 Å resolution X-ray diffraction data set was collected from native N-terminally truncated PilA (ΔN-PilA). Data proces ...[more]

PMID: 22442223

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Project description:UnlabelledNontypeable Haemophilus influenzae (NTHI), a commensal of the human nasopharynx (hNP), is a common cause of biofilm-associated diseases of the respiratory tract. However, NTHI biofilm biology at the average hNP temperature, i.e., 34°C, has not been well studied. Here we grew NTHI biofilms at 34°C and 37°C, to evaluate relative biofilm growth, expression, and function of the type IV pilus (Tfp), a critical adhesin important for NTHI biofilm formation. The kinetics and regulation of Tfp expression in NTHI biofilms are unclear, especially at 34°C. Tfp expression, as estimated by pilA promoter activity, was distributed throughout the biofilms, with a unique pattern that was dependent on temperature, time in culture, and position within the maturing biofilm. Tfp expression was required for the formation of the characteristic tower structures of NTHI biofilms and was significantly upregulated in NTHI biofilms formed at 34°C versus 37°C. This increase correlated with significantly greater twitching motility at 34°C than at 37°C. Treatment with antisera targeting the major subunit of Tfp (PilA) significantly inhibited NTHI biofilm formation at both temperatures, confirming the importance of this critical adhesin in biofilm formation. Additionally, treatment of preestablished biofilms with antisera against PilA significantly decreased biofilm biomass and mean thickness at both temperatures. These results demonstrated a pivotal role for Tfp in NTHI biofilm formation and stability at the temperature of the hNP, and they underscore the utility of PilA as a vaccine candidate for treatment and/or prevention of NTHI biofilm-associated diseases.ImportanceNTHI is an important cause of chronic respiratory tract infections, including otitis media, chronic rhinosinusitis, and exacerbations of chronic obstructive pulmonary disease and cystic fibrosis. The chronic and recurrent nature of these diseases is attributed to the presence of bacterial biofilms, which are highly resistant to antimicrobials. We characterized NTHI biofilm growth and expression of PilA, the major subunit of the Tfp, at the temperature of the hNP, which is the commensal habitat of NTHI. Our results expand the current understanding of the role of Tfp during biofilm formation and maturation at the temperature of both the hNP and the middle ear, and they strengthen support for PilA as a vaccine candidate for the prevention and treatment of NTHI biofilm-associated diseases.

Project description:A subset of nontypeable Haemophilus influenzae (NTHI) biotype IV isolates from the human genital tract or from infected newborn infants forms a cryptic genospecies characterized by, among other features, the presence of peritrichous pili. The objective of this study was to determine the similarity of these pili to hemagglutinating, HifA- and HifE-containing pili expressed by respiratory H. influenzae isolates. For this analysis, the presence of hifA and hifE and their gene products in NTHI biotype IV strains was assessed, the binding of H. influenzae biotype IV strains to human epithelial cells was characterized, possible genital tissue tropism of these isolates was explored, and the role of HifA- and HifE-possessing pili in the adhesion of NTHI biotype IV strains to human epithelial cells was determined. None of the six biotype IV NTHI isolates tested agglutinated human red blood cells, nor could they be enriched for hemagglutinating variants. Although hifA, which encodes the major structural subunit of hemagglutinating pili, and hifE, which encodes the tip adhesin of hemagglutinating pili, were detected by PCR from six and five, respectively, of the six biotype IV strains tested, neither HifA nor HifE (the gene products of hifA and hifE) were detected in any of these strains by Western blot analysis using antisera that recognize HifA and HifE of respiratory strains. Transmission electron microscopy showed no surface pili on the two biotype IV H. influenzae isolates examined; strain 4162 containing an insertional mutation in hifA also showed no surface pili, whereas strain 1595 containing an insertional mutation in hifB showed pilus-like structures that were shorter and thicker than hemagglutinating pili of the respiratory strains AAr176 and M43. In enzyme-linked immunosorbent assays, biotype IV strains adhered to 16HBE14o(-) and HEp-2 cells of respiratory origin as well as to ME180 and HeLa cells of genital origin. This adherence was not pilus specific, however, as GM-1, a known pilus receptor analog, did not inhibit binding of biotype IV strains to ME180, HEp-2, or HeLa cells, and GM-1 inhibition of binding to 16HBE14o(-) cells did not correlate with the presence of hifE. While both nonpiliated variants and hifA and hifB (encoding the pilus chaperone) mutants of respiratory strain AAr176 showed reduced binding (64 to 87% of that of piliated AAr176) to 16HBE14o(-) and ME180 cells, hifA and hifB mutants of the biotype IV strains showed minimal reduction in binding to these cell lines (91 to 98% of that of wild-type strains). Thus, although biotype IV H. influenzae isolates of the cryptic genospecies possess the genes that code for HifA- and HifE-containing hemagglutinating pili, epithelial cell adherence exhibited by these strains is not mediated by expression of hemagglutinating pili.

Dataset Information

Expression, purification, crystallization and preliminary crystallographic analysis of PilA from the nontypeable Haemophilus influenzae type IV pilus.

Publications

Expression, purification, crystallization and preliminary crystallographic analysis of PilA from the nontypeable Haemophilus influenzae type IV pilus.

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