Intact proinsulin, des 31,32 proinsulin, and specific insulin concentrations among nondiabetic and diabetic subjects in populations at varying risk of type 2 diabetes |
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Authors: | DK Nagi WC Knowler V Mohamed-Ali PH Bennett JS Yudkin |
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Affiliation: | Department of Chemistry, Auburn University, Alabama 36849-5312, USA. werneca@mail.auburn.edu |
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Abstract: | Starting with crude yeast mitochondria, the intron homing endonuclease, I-SecIV, was purified to near homogeneity. This highly purified enzyme differs from some other well-characterized yeast mitochondrial intron-encoded endonucleases in terms of its structure and DNA cleavage specificity. The enzyme is a heterodimer with a native molecular mass of 92 kDa. A small catalytic subunit (32 kDa) is probably encoded largely or entirely by intron 5 alpha of the cytochrome oxidase subunit I gene. A larger polypeptide subunit (60 kDa) may be a nuclear factor necessary for intron mobility. I-SceIV exhibits a low DNA sequence specificity as it cleaves a variety of DNA substrates. Analysis of kinetic parameters shows that the purified enzyme has a very high affinity for DNA and exhibits low turnover which may have implications for subsequent steps in the intron homing process. |
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