GTPase family

Dynamin, unlike many GTPase superfamily members, exhibits a relatively rapid basal rate of GTP hydrolysis that is not rate-limited by GTP binding or GDP dissociation. Also unique to dynamin GTPase family... 

Small GTPases of the Rho family are ADP-ribosylated (e.g., at Asn4l of RhoA) and inactivated by C3-like toxins from Clostridium botulinum, Clostridium limosum, and Staphylococcus aureus. These proteins have a molecular mass of 23-30 kDa and consist only of the enzyme domain. Specific inhibition of Rho functions (Rho but not Rac or Cdc42 are targets) is the reason why C3 is widely used as a pharmacological tool [2]. 

The above mentioned Rho GTPases are glucosylated by the family of clostridial glucosylating cytotoxins. 

A subfamily of Rho proteins, the Rnd family of small GTPases, are always GTP-bound and seem to be regulated by expression and localization rather than by nucleotide exchange and hydrolysis. Many Rho GTPase effectors have been identified, including protein and lipid kinases, phospholipase D and numerous adaptor proteins. One of the best characterized effector of RhoA is Rho kinase, which phosphorylates and inactivates myosin phosphatase thereby RhoA causes activation of actomyosin complexes. Rho proteins are preferred targets of bacterial protein toxins ( bacterial toxins). 

SARA is a scaffolding protein that regulates the subcellular localization of inactivated R-Smads, potentially scaffolding the TGF-P receptor kinase to the Smad 2 substrate. Filamins are a family of actin polymerization proteins that also form scaffolds for a range of signaling proteins including SAP kinases such as MKK-4, small GTPases Rho and Ras, as well as Smad 2 and Smad 5. 

---