Muscle cells have an abundant, modified smooth ER called the sarcoplasmic reticulum.

The release and reuptake of Ca2+ by the sarcoplasmic reticulum trigger myofibril contraction and relaxation, respectively

TLS Online TPP Program

#Id: 10010

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Two membrane proteins, 

Smoothened (Smo) 

Patched (Ptc)

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#Id: 10011

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Smo has seven TM α helices, is a member of the GPCR superfamily, and is related in sequence to the Fz.

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#Id: 10012

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Ptc contains 12 TM α helices and structurally similar

to the Niemann-Pick C1 protein, a cholesterol transporting member of the ABC superfamily

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#Id: 10013

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In the absence of Hh,

Ptc inhibits Smoothened and then degraded in proteasomes

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#Id: 10014

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Transcription Factor

zinc-finger transcription factor Cubitis interruptus

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#Id: 10015

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A cytosolic complex contains

kinases Fused ; PKA, GSK3β, and CK1, Ci, and SUFU