Structure of Src tyrosine kinase
   
Basic structure: 
The Src protein includes an N-terminal region that is covalently bonded to a very hydrophobic fatty acid.   This linkage attaches the kinase onto the cytoplasmic side of the cellular membrane.  The SH3 and SH2 domains are two molecules that bind peptides.

structure of protein

 Figure (A) is a ribbon model of the Src protein.  Figure (B) is a spherical model of the same Src protein.  Two of the domains, the small kinase domain and the large kinase domain, form a protein kinase enzyme.  The other two domains, SH2 and SH3, perform regulatory functions.  In both models, the ATP substrate is shown in red.  (Figure and information taken from Molecular Biology of the Cell, Alberts, 2002).
Activating Src Tyrosine kinase:
             
                              ACTIVE FORM                      INACTIVE FORM



activation of src
                               
The Src protein undergoes a particular process in order to activate itself.  The structure shown above on the right represents the inactive form, while the structure on the left represents the active form.  As seen in the active form, the Src protein consists of several functioning units that are connected to one another.  The most important factor in the "opening" and "closing" of this protein involves the tyrosine residue found in the tail portion of the active form; this tyrosine residue is shown in blue.  When this tyrosine residue becomes phosphorylated, it binds with the SH2 domain and, in essence, "glues" the protein shut.  Upon removal of the phosphate group, the protein opens up, causing the protein to take on it's active form.  (Figure and information taken from Protein Data Bank Molecule of the Month, Goodsell, 2003).


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