Larry J. Takemoto

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Gap junctions are composed of a family of structural proteins called connexins, which oligomerize into intercellular channels and function to exchange low molecular weight metabolites and ions between adjacent cells. We have cloned a new member of the connexin family from lens cDNA, with a predicted molecular mass of 46 kD, called rat connexin46 (Cx46).(More)
Abietane diterpenoids are major constituents of conifer resins that have important industrial and medicinal applications. However, their function in plants is poorly understood. Here we show that dehydroabietinal (DA), an abietane diterpenoid, is an activator of systemic acquired resistance (SAR), which is an inducible defense mechanism that is activated in(More)
PURPOSE To identify and quantitate deamidation of a specific asparagine residue of gammaS-crystallin that preferentially undergoes deamidation during the process of human senile cataractogenesis. METHODS Reverse phase chromatography, together with synthetic peptide standards, was used to resolve the amidated and deamidated forms of asparagine-143 in the(More)
Although proteins are generally composed entirely of l-amino acids, we have previously shown that Asp-151 in alphaA-crystallin from aged human lens is converted to the biologically uncommon d-isomer to a high degree. The formation of d-isomer was not simple racemization, but stereoinvertion. The reaction was also accompanied with isomerization to form(More)
Although it has been hypothesized that age-dependent deamidation of glutamine and/or asparagine residues may play an important role in the turnover of proteins in vivo, surprisingly little is known concerning the extents of deamidation of biologically important proteins with very long half-lives. Alpha-A crystallin is the most abundant protein of the adult(More)
Total alpha-A crystallin was purified from young versus old lens, followed by digestion with cyanogen bromide. Laser desorption mass spectrometry of the C-terminal fragment demonstrated age-dependent loss of one and five amino acids from the C-terminus of alpha-A crystallin from both bovine and human lens. These results demonstrate specific peptide bonds of(More)
Using the techniques of high performance liquid chromatography (HPLC), gel electrophoresis in the presence of sodium dodecyl sulfate (SDS), and immunoblotting, we have analyzed the age-related changes in soluble crystallins of the human lens. A 3 mm core along the optical axis of each lens was frozen-sectioned and the sections were biochemically analyzed(More)
Although it has been known for many years that opacification of the human lens is accompanied by oxidation of cysteine sulfhydryl groups to half-cystine residues, nothing is known concerning the exact amino acid sequences involved in this oxidative process. Since alpha-A crystallin is one of the major proteins of the lens, and since a decrease in its(More)
At high protein concentrations found in the lens, short-range order of lens proteins results in a medium of relatively constant protein density and refractive index that minimizes scattering of light. During aging and cataractogenesis of the lens, formation of high molecular weight aggregates causes fluctuations in this protein density, resulting in light(More)
Past studies have identified posttranslational modifications of human lens proteins occurring during cataract formation, and have also demonstrated that protein-protein interactions exist between different lens crystallins. Based upon current theories of lens transparency, these posttranslational modifications and their possible effects upon crystallin(More)