Analysis of the molecular mass heterogeneity of the transferrin receptor in Neisseria meningitidis and commensal Neisseria.

Peroxidase-conjugated transferrin was used to detect transferrin receptors both in intact outer membrane vesicles (OMVs) from Neisseria species in a dot blot assay, and in SDS-PAGE-separated OMV proteins after transferring to nitrocellulose membranes. All N. meningitidis strains produced transferrin receptors after culturing in either iron sufficiency or iron restriction although expression was higher in the latter case, whereas only six N. lactamica and two N. sicca (among 20 commensal species) were able to bind transferrin. Molecular mass (MM) of the receptors were mainly between 78 kDa and 85 kDa (87.5% of strains), 12.5% had receptors with MM close to 70 kDa, and 5% showed receptors with MM over 85 kDa. Our results confirm the molecular mass heterogeneity of the transferrin receptors in N. meningitidis, completely disagree with the 'universal' 98 kDa receptor proposed by some authors, and show a low expression of the receptor in commensal Neisseria.