Aberrant cGMP-binding activity in non-chemotactic Dictyostelium discoideum mutants

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• 作者：Kuwayama ; Hidekazu ; Viel ; Gerhard T. ; Ishida ; Shuji ; Van Haastert ; Peter J.M.
• 关键词：Cyclic adenosine 3&prime ; 5&prime ; -monophosphate ; cyclic guanosine 3&prime ; 5&prime ; -monophosphate
• 刊名：Biochimica et Biophysica Acta (BBA)/Molecular Cell Research
• 出版年：1995
• 出版时间：August 31, 1995
• 年：1995
• 卷：1268
• 期：2
• 页码：214-220
• 全文大小：616 K

文摘

The kinetics of cGMP-binding to the major cGMP-binding activity in Dictyostelium were investigated in 10 non-chemotactic mutants (KI mutants; KI-1 10). A wild-type cell contains about 3000 binding sites with a K_d of 1.5 nM. cGMP may dissociate from these binding sites with fast (F-type) or slow (S-type) kinetics, and DNA has been shown to promote the conversion of F- to S-type of cGMP-binding. The 10 mutants were placed in 4 classes, based on equilibrium and non-equilibrium binding properties and the effect of DNA. Class I mutants (KI-1, 3 and 8) have normal cGMP-binding properties. Class II mutants (KI-2, 6 and 7) show increased K_d values but nearly normal B_max, normal ratio and normal effects of DNA. Class III mutants (KI-4, 5 and 10) have a strongly decreased K_d and increased B_max, nearly all binding sites are of the S-type and DNA does not affect the binding; apparently these mutants have a cGMP-binding protein locked in the S-form. cGMP-binding in class IV mutant (KI-9) is normal except that the number of binding sites is increased about 3-fold. The finding of seven mutants with altered cGMP-binding in 10 non-chemotactic mutants suggests that the cGMP-binding activity plays an important role in the chemotactic signal transduction pathway.