PROINSULIN: CRYSTALLIZATION AND PRELIMINARY X-RAY DIFFRACTION STUDIES

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Abstract
Bovine proinsulin has been crystallized under a variety of conditions at both neutral and acid pH. Microtechniques were employed with sample weights of about 200 μg and volumes of 5-20 μl. The crystalline preparations all differ from each other morphologically. X-ray photographs of one form, tetragonal bipyramids grown at pH 3 with added ammonium sulphate solution, established the space group P4 1 2 1 2 (or its enantiomorph P4 3 2 1 2). The cell dimensions are a = 50.8 ± 0.2 Å, c = 148.0 ± 0.4 Å. The asymmetric unit in this form is a dimer of proinsulin which is also the dominant species in solution at this pH.