Term of Award

Summer 2011

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Department

Department of Biology

Committee Chair

James Claiborne

Committee Member 1

Laura Regassa

Committee Member 2

Danny Gleason

Abstract

Sodium hydrogen exchanger proteins (NHEs) are members of the cation proton antiporter superfamily (CPA) and are thought to function in fish for maintaining physiological ion concentrations and acid-base balances by excreting excess H+ ions from the body in exchange for Na+ ions. There are many more types of these proteins in teleost fish than in mammals due to putative genome duplication. This study describes a new form of NHE2 in the gills of marine longhorn sculpin, Myoxocephalus octodecemspinosus, designated NHE2c. Sequencing revealed that the NHE2c nucleotide-coding region transcribes a peptide 795 amino acids in length with an estimated molecular weight of 89.2 kDa. Data shows that NHE2c is a unique peptide from previously described NHE isoforms, including the NHE2 family. A polyclonal antibody made against NHE2c and used in double and triple labeled immunohistochemical experiments detected the peptide on the apical edge of gill cells that also contained Na+-K+-ATPase and NHE2b. Western blot analysis detected two protein bands at approximately 45 kDa and 75 kDa. These extra copies of NHE2 in the sculpin genome pose an intriguing question of why the proteins are synthesized in the first place. While, in the future, studying syntenic NHE paralogs in the NHE2 family of longhorn sculpin could give us an evolutionary perspective to homologous NHEs in higher vertebrates.

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