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Title: CHARACTERIZATION OF A PERIPLASMIC 31-KILODALTON IRON-REGULATED PROTEIN FROM PASTEURELLA HAEMOLYTICA A1

Author
item Tabatabai, Louisa
item Frank, Glynn

Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pasteurella haemolytica serotype A1 causes respiratory disease (shipping fever) in calves which cost the livestock industry close to 1 billion dollars, annually. The research focuses on the identification and purification of proteins with vaccine potential. It is anticipated that those proteins which allow the pathogen to survive in the calf should be excellent vaccine candidates. An efficacious multi-component protein-derived vaccine administered before or at the point of sale would enhance resistance of the calves to Pasteurella infection during shipping to the feedyard and therefore cut economic losses to the livestock industry due to shipping fever.

Technical Abstract: P. haemolytica expressed three iron-regulated periplasmic proteins with molecular weights of 31,000, 35,000 and 42,000 Daltons. We describe the purification and characterization of the 31 kDa periplasmic iron-regulated protein from Pasteurella haemolytica A1. The N-terminal sequence, EPFKVVTTFTVIQDIAQNVAGDKAT, has a 95% identity with the 31 kDa iron-repressible N-terminal protein fragment from Haemophilus influenzae. The molecular mass of the protein was determined by SDS-PAGE (32,000) and matrix-assisted laser desorption mass spectrometry (30,784). The molecular mass obtained by equilibrium velocity (29,877) also indicated that the protein exists as a monomer in its native state. the isoelectric point of the 32 kDa protein was 7.0. The secondary structure as determined by circular dichroism was typical of à-helical with á-strand structure. The 31 kDa protein was present in extracts of P. haemolytica grown under iron deficient conditions, whereas expression of the 31 kDa protein was reduced when the organisms were grown under iron replete conditions, suggesting protein expression is iron-regulated. Furthermore, the protein is recognized by serum from calves infected with P. haemolytica and by sera from convalescent calves. The role of the 31 kDa protein in iron assimilation by P. haemolytica is not known.