This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Lange-Carter, C. A. Articles by Malkinson, A. M. Search for Related Content PubMed PubMed Citation Articles by Lange-Carter, C. A. Articles by Malkinson, A. M.

Growth Rate Dependence of Differential Incorporation of a Guanosine Triphosphate Photoaffinity Probe into the Subunit of a Guanine Nucleotide Binding Protein, G_s, from Metastatic Variants of B16 Melanoma Cells¹

Molecular and Environmental Toxicology Program, School of Pharmacy, University of Colorado, Boulder, Colorado 80309-0297 [C. A. L-C., K. A. D., A. M. M.], and Department of Laboratory Medicine and Pathology, Dight Laboratories, University of Minnesota, Minneapolis, Minnesota 55455 [B. R. L.]

The signal transducing regulatory protein (G_s) was examined in B16 melanoma clones of low (F1C29) and high (F10C23) experimental metastatic potential. Incorporation of the photoaffinity analogue, [8-azido--³²P]GTP, into G_s was decreased in F10C23 extracts when compared to F1C29. This difference disappeared when the photolabeling reaction was carried out at an elevated temperature which enhanced the rate of GTP exchange, suggesting functional differences in the ability of G_s to bind or release GTP rather than dissimilar intracellular G_s concentrations. Differential G_s photolabeling occurred only during the period of rapid growth when F10C23 cells proliferated faster than F1C29 cells. During the recovery phase of growth immediately following plating and at confluence, periods in which F1C29 and F10C23 growth rates are similar, G_s photolabeling between the two clones was equal. CMT lung carcinoma clones of differential metastatic potential grew at a uniform rate at all stages of growth and also exhibited equal G_s photolabeling. F10C23 cells were more responsive to -melanocyte-stimulating hormone stimulation of adenylate cyclase activity than F1C29 cells at all growth stages. These results confirm previously observed functional differences in G_s between B16 metastatic variants and show that photolabeling differences in G_s are related to growth rate.

¹ Supported by USPHS Grants ES02370 and HL37718; Research Career Development Award CA-00939 (to A. M. M.); American Cancer Society Grant IN-13-Z28; and a Leukemia Task Force grant (to B. R. L.).

² To whom requests for reprints should be addressed.

Received 9/ 2/88. Revised 1/27/89. Accepted 3/17/89.