Receptor phosphorylation is a key step in the process of rapid desensitization. beta-adrenergic receptor kinase (betaARK) is a specific receptor kinase that is known to phosphorylate and induce desensitization of several G-coupled receptors only when they are occupied by their agonists. In the present study we have done several modifications to the amino-terminal of betaARK1, in order to clarify its functional role. The recombinant mutants were tested for their ability to phosphorylate rhodopsin present in purified bovine ROS membranes which serves as a substrate for betaARK1. Their expression levels were detected by Western blot analysis. We found that when the amino-terminal of betaARK1 is modified its expression level is very low, hence it is not able to phosphorylate over the basal. These findings suggest that this region is crucial for the normal processing of the protein.