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M Imagawa

Publications and source records attributed to M Imagawa.

167 records · Page 10Linked to original sources
PubMedDate not supplied

Multiple cis- and trans-acting elements mediate the transcriptional response to phorbol esters.

Protein kinase C is important in the transduction of signals generated at the plasma membrane. The physiological activators of protein kinase C are diacylglycerols, and the tumour-promoting phorbol esters, such as 12-O-tetradecanoyl-phorbol-14 acetate (TPA), constitute another group of specific activators. Many cellular substrates for phosphorylation by protein kinase C have been described, but proteins that directly control transcription in response to protein kinase C activation are yet to be identified. TPA treatment leads to induction of various proto-oncogenes, growth factor genes, and genes encoding secreted proteases. In addition. TPA increases the activity of viral enhancer elements. To identify trans-acting factors that mediate the transcriptional response to TPA we chose the simian virus 40 (SV40) enhancer as a model, because it is known to be composed of several discrete cis-acting elements which are recognized by multiple transacting factors. We report here that the SV40 enhancer contains at least four different TPA responsive elements whose activity is dependent on cell-type. The induction response is likely to involve at least two distinct post-translational steps which modulate the activity of the proteins that recognize these elements.

Base Sequence↗
PubMedDate not supplied

More useful maleimide compounds for the conjugation of Fab' to horseradish peroxidase through thiol groups in the hinge.

Nine different maleimide compounds were evaluated for the conjugation of Fab' to horseradish peroxidase through thiol groups in the hinge. The compounds evaluated were succinimidyl maleimidoacetate (I), succinimidyl 4-maleimidobutyrate (II), succinimidyl 6-maleimidohexanoate (III), succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (IV), succinimidyl m-maleimidobenzoate (V), succinimidyl 4-(p-maleimidophenyl)butyrate (VI), sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (VII), sulfosuccinimidyl m-maleimidobenzoate (VIII), and sulfosuccinimidyl 4-(p-maleimidophenyl)butyrate (IX). Maleimide groups of I-IV and VII were fairly stable at pH 7.0 at 30 degrees C, while those of the other compounds were significantly decomposed. I-III and VII-IX were sufficiently soluble in the reaction mixture for the introduction of maleimide groups, while the others were more or less precipitated during the reaction. II and III were the most effective in the introduction of maleimide groups and gave the highest recovery of peroxidase in the conjugate, which reached 80%. From these results, II and III were judged to be the most useful, and IV and VII were judged to be fairly useful.

Horseradish Peroxidase↗