Myocardial fibers have a resting membrane potential of approximately –90 mV.

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#Unit 4. Cell Communication and Cell Signaling

PI-3 kinase adds a phosphate to the 3′ carbon in one of two separate PI substrates, leading to formation of two PI 3-phosphates: PI(3,4)P2 or PI(3,4,5)P3

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#Unit 4. Cell Communication and Cell Signaling

In cells, PI-3 kinase pathway :

Triggers cell division 

Prevents apoptosis

Induces specific changes in cell metabolism

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#Unit 4. Cell Communication and Cell Signaling

An important signal transduction protein that binds to PI 3-phosphates is protein kinase B (Akt),  a serine/threonine kinase

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#Unit 4. Cell Communication and Cell Signaling

PI-3 kinase was first identified in studies of the 

polyoma virus, a DNA virus

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#Unit 4. Cell Communication and Cell Signaling

PKB contains:

A PH domain

A kinase domain

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#Unit 4. Cell Communication and Cell Signaling

PH domain of PKB binds with high affinity to the 

3-phosphates in both PI(3,4)P2 and PI(3,4,5)P3