Theses and Dissertations
Issuing Body
Mississippi State University
Advisor
Pharr, G. Todd
Committee Member
Hanson, Larry A.
Committee Member
Boyle, John A.
Committee Member
Lawrence, Mark L.
Committee Member
Branton, Scott L.
Date of Degree
8-3-2002
Document Type
Dissertation - Open Access
Major
Veterinary Medical Science
Degree Name
Doctor of Philosophy
College
College of Veterinary Medicine
Department
Veterinary Medical Science Program
Abstract
Unlike most other host-specific mycoplasmas, Mycoplasma gallinarum exists as a commensal with a host range including most poultry as well as some mammals. This property of M. gallinarum may reflect unique mechanisms for its colonization and persistence in hosts. Whereas M. gallinarum shows leucine and arginine aminopeptidase activity, the genes encoding the enzymes had not been cloned and characterized. We identified an aminopeptidase gene (APN) by oligonucleotide hybridization to a genomic library of M. gallinarum in lambda ZAPII bacteriophage. Nucleotide sequence analysis of overlapping phage clones identified a 1,362 bp open reading frame (ORF) encoding a putative leucine aminopeptidase gene. Database searches indicate that this ORF has 68% nucleotide identity and 51% amino acid identity with the M. salivarium leucine aminopeptidase gene. The active sites of the leucine aminopeptidases in other eukaryotes and prokaryotes were conserved in the cloned aminopeptidase gene. Northern-blot hybridization analysis showed that this ORF is expressed as a 1.5 kb transcript. Southern-blot hybridization analysis demonstrated this gene was present as a single copy in M. gallinarum. Characterization of the leucine aminopeptidase demonstrated that it is a metallo-aminopeptidase (EC 3.4.11.1) and is located in the cytoplasm with a weak interaction with the cell membrane. The subcellular location was further confirmed by immunoblotting with polyclonal anti-recombinant APN serum and M. gallinarum Triton-114 partitions. Immunoblotting results with sera from three chickens experimentally infected with M. gallinarum showed that there were very few proteins in M. gallinarum exposed to the host immune responses and that leucine aminopeptidase was not able to stimulate production of specific humoral antibody. Our results suggest that this leucine aminopeptidase play a role in nutrition supply for the host adaptation of M. gallinarum and that the enzyme was not strongly immunogenic.
URI
https://hdl.handle.net/11668/20965
Recommended Citation
Wan, Xiufeng, "An Aminopeptidase Acting as a Potential Factor in Host Adaptation of Mycoplasma Gallinarum" (2002). Theses and Dissertations. 454.
https://scholarsjunction.msstate.edu/td/454