Vertebrate skeletal muscle contraction, also depends on set of specialized accessory proteins that are closely associated with the actin thin filaments:

a) Tropomyosin

b) Troponin

TLS Online TPP Program

#Id: 9362

#XL - T Zoology

MH1 domain contains:

DNA binding segment Nuclear-localization signal

TLS Online TPP Program

#Id: 9363

#XL - T Zoology

Phosphorylation of two serines in Ser-X-Ser motif at the extreme C-terminus of the MH2 domain by the activated RI separates the two domains, exposing the NLS for binding to importins

TLS Online TPP Program

#Id: 9364

#XL - T Zoology

Simultaneously, two serines in each Smad2/3 phosphorylated by RI receptor kinase bind to phosphoserine-binding sites in the MH2 domains of a Smad4

TLS Online TPP Program

#Id: 9365

#XL - T Zoology

Inside the nucleus, R smad-co smad complex binds to nuclear transcription factor TFE3 to activate transcription of PAI-1 & other ECM proteins such as fibronectin & collagens

TLS Online TPP Program

#Id: 9366

#XL - T Zoology

Within the nucleus, R-Smads are modified by:

Phosphorylation of linker domains

Acetylation of MH1 domains

Dephosphorylation of the C-terminal serines by nuclear

phosphatases

TLS Online TPP Program

#Id: 9367

#XL - T Zoology

BMP proteins, activate a different set of receptors that are similar to the TGF-β RI and RII proteins but phosphorylate other R-Smads, Smad1, Smad5, & Smad8