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A Monoclonal Antibody Which Identifies the Autophosphorylation Domain of Autophosphorylating Protein Kinase 500¹

Section of Regulatory Biology, Cleveland Clinic Research Institute, Cleveland, Ohio 44195-5068 [R. K. S.], and the Departments of Physiology and Biophysics, and Biochemistry [G. M., W. E. J.], University of Tennessee, Memphis, Memphis, Tennessee 38163

Autophosphorylating protein kinase 500 is a serine protein kinase expressed progressively with the steps of cellular transformation, approaching levels from 50- to 100-fold in the terminal stages of malignancy. the enzyme possesses a sharply restricted range of substrates: itself and a ribosomal protein with a molecular weight of 31,000 (S6). We report here on the characterization of a monoclonal antibody directed against the autophosphorylation domain of AUT-PK 500. The specificity of the antibody is evidenced by blockage of the enzyme phosphorylation without interfering with the native S6 or synthetic octapeptide (S6-1) serine residue phosphorylations. This represents an important step in identifying a probe that can be used to explore the structure and potential function of AUT-PK 500 in cellular transformation.

¹ This investigation was supported by NSF Grant DCB-8609867 and NIH Grant NS-23744.

² To whom requests for reprints should be addressed, at Section of Regulatory Biology, Department of Brain and Vascular Research, The Cleveland Clinic Research Institute, 9500 Euclid Avenue, Cleveland, OH 44195.

Received 3/16/88. Revised 9/21/88. Revised 12/ 6/88. Accepted 12/19/88.