作者: C. B. Klee
DOI: 10.1021/BI00624A033
关键词:
摘要: The Ca2+-dependent protein activator of 3':5'-cyclic adenosine monophosphate phosphodiesterase is shown to undergo a conformational transition upon binding 2 mol Ca2+/mol activator. Circular dichroic studies indicate that Ca2+ induces an increase 5-8% in alpha-helix content with concomitant decrease the amount random coil. In absence and presence [ethylenebis(oxoethylenenitrilo)]tetraacetic acid (EGTA), contains 30-35% alpha helix, 50% coil, 15-20% beta-pleated sheat. Spectrophotometric titration indicates two tyrosyl residues have pK's 10.4 11.9 are therefore different environments. Ca2+-induced change accompanied by increased exposure protons partially exposed tyrosine, as shift its pK from 10.). Increased solvation also consistent negative difference spectrum at 287 279 nm seen binding. Modification environment all or some phenylalanine part accompanying A new rapid purification procedure which yields large amounts (25-30% yields) homogenous direct sensitive assay for cAMP described.