Structural Analysis of TGFb138

 

Structure

The transforming growth factor beta (TGFb) signaling pathway orchestrates an enormous range of biological processes and is the target of numerous drug development efforts. These efforts have focused on modulating several layers of the signaling cascade, including the ligand-receptor complex and the intracellular receptors. Structural studies have consolidated existing TGFb-related structural knowledge and provided a platform for future mechanistic investigations of the cascade at the cellular level.

Recent crystal structures of the type I TGFb receptor kinase domains have revealed that two distinct salt bridges formed between Glu245 on the aC helix and Lys232 on b3 contribute to constitutive activation. Moreover, structural studies have allowed the direct comparison of these structures to the activity of FKBP12-binding mutations that cause abnormal receptor activation, highlighting how these mutations directly impact kinase function.

CCDC138 is predicted to have a number of alpha helixes, beta sheets, and coiled-coils by PELE, CHOFAS, and GOR4. It contains an Asparagine at beta 138 which, when replaced with Pro, causes the unstable hemoglobin variant Hb Brockton that exhibits low oxygen affinity.

Electrophoretic Mobility

The electrophoretic mobility of an Bet138 analyte is a measure of its rate of traversal of a particular distance during electrophoresis. It depends on the magnitude of the electric field and the size and charge of the analyte, as well as the viscosity of the sample medium.

Hemoglobin Brockton [beta 138 (H16) Ala----Pro] has the same electrophoretic mobility as Hb A and cannot be differentiated from it by any of the usual methods. This suggests that the proline substitution does not affect the critical inter- and intrasubunit hydrogen bonds and salt bridges of the beta carboxyl terminus or helix.

Satisfactory separation of haemoglobins can usually be obtained by acid agarose gel electrophoresis and HPLC or IEF. However, differences in electrophoretic mobility do not always permit satisfactory differentiation between cis/trans isomers and diastereomeric Marfey's derivatives of enantiomers. This is because differences in internal hydrogen bonding interactions between the enantiomers can cause them to have different electrophoretic mobilities.