Proteins structure transcription

Small tfbiquitin-like modifier represents a family of evolutionary conserved proteins that are distantly related in amino-acid sequence to ubiquitin, but share the same structural folding with ubiquitin proteins. SUMO proteins are covalently conjugated to protein substrates by an isopeptide bond through their carboxyl termini. SUMO addition to lysine residues of target proteins, termed SUMOylation, mediates post-transla-tional modification and requires a set of enzymes that are distinct from those that act on ubiquitin. SUMOylation regulates the activity of a variety of tar get proteins including transcription factors. 

The identified genes code for a variety of proteins, including transcription factors that are important for inner-ear development, cytoskeleton proteins that are responsible for the specialized architecture of hair cells, extracellular matrix molecules that make up some of the specialized acellular structures of the inner ear, and still others whose function is not yet clear. 

That is transcription. Now, we get on with the final step the translation of mRNA structure into protein structure. 

Protein Features of protein structure Effect on transcription Other properties In vivo expression and localization... 

Heim, M.A., et ah, The basic helix-loop-helix transcription factor family in plants a genome-wide study of protein structure and functional diversity. Mol Biol Evol, 20, 735, 2003. 

Leucine zipper proteins. Several transcription factors have the leucine zipper structure, which has been described in Chapter 2 and was illustrated there by the structure of transcription factor Max (Fig. 2-21).417 Related structures include those of the transcription... 

Two types of control are illustrated. On the left, the inducer acts by inactiviating a repressor protein allowing transcription of the structural genes. On the right, a repressor combines with an aporepressor protein to form an active repressor complex which blocks transcription of the structural genes... 

HSF3, identified in chicken, is induced by c-Myb in the absence of cellular stress (Nakai and Morimoto, 1993 Kanei-Ishii et al., 1997). Another isoform of HSF found in human cells, HSF4, possesses transcription represser properties in vivo (Frejtag et al., 2001). Comparisons of HSF protein structure in these organisms indicate the presence of conserved DNA binding domain and three hydrophobic heptad repeats that constitute the trimerization domain. These domains are located within the amino-terminal region of the protein. The stress-responsive transcriptional activation domain is located in the carboxyl-terminal region of the molecule. 

Transcription factors that increase the rate of transcription usually have at least two domains of protein structure, a DNA-binding domain that recognizes the specific DNA control element to bind to, and an activation domain that interacts with other transcription factors or the RNA polymerase. Many transcription factors operate as dimers (homodimers or heterodimers) held together via dimerization domains. Some transcription factors interact with small ligands via a ligand-binding domain. 

---