. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SIGNALING IN GVBD 97 . Pro-MPF synthesis Pi mactivation Amino Acids Phosphatase. Kinase MPF amplification Lamm, Histone Kinases Figure 1. Scheme showing the proposed metabolism of MPF. MPF is synthesized as a precursor (Pro-MPF) which is activated by phos- phorylation catalyzed by one or more protein kinases. It then amplifies its activity autocatalytically by autophosphorylation. It also activates other kinases (, lamin and histone kinases) responsible for nuclear protein phosphorylation. It could be inactivated by deph
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SIGNALING IN GVBD 97 . Pro-MPF synthesis Pi mactivation Amino Acids Phosphatase. Kinase MPF amplification Lamm, Histone Kinases Figure 1. Scheme showing the proposed metabolism of MPF. MPF is synthesized as a precursor (Pro-MPF) which is activated by phos- phorylation catalyzed by one or more protein kinases. It then amplifies its activity autocatalytically by autophosphorylation. It also activates other kinases (, lamin and histone kinases) responsible for nuclear protein phosphorylation. It could be inactivated by dephosphorylation or by proteolytic degradation. Heavy lines terminating in arrows repre- sent an activation process. Thin lines terminating in arrows represent chemical conversions. Italicized words indicate what is happening to MPF at each stage in the scheme. phosphatases strongly indicates that MPF should be a protein kinase. A scheme for the metabolism of MPF and its involve- ment in GVBD is shown in Figure 1. In this model. MPF is synthesized as an inactive precursor, Pro-MPF. It be- comes active upon phosphorylation. MPF has kinase ac- tivity and amplifies its activity by autophosphorylation. It then activates other kinases which directly phosphory- late nuclear proteins, leading to nuclear envelope break- down and chromosome condensation. MPF could be in- activated by dephosphorylation or by proteolytic degra- dation. The mechanisms involved in the initial appearance of MPF remain to be explained. Clearly, though MPF can be amplified autocatalytically, its initial activity must be turned on or activated by some process derived from ear- lier events in the GVBD triggering process. Since MPF amplification is invariably associated with protein phos- phorylation and MPF is stabilized by phosphatase inhib- itors, its initial activation probably involves phosphory- lation as well. It is not known which if any specific phos- phorylation sites on the molecule are essential for its
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
