IMMUNOFLUORESCENCE STUDIES OF HUMAN FIBROBLASTS DEMONSTRATE THE PRESENCE OF THE COMPLEX OF ELONGATION FACTOR-1-BETA-GAMMA-DELTA IN THE ENDOPLASMIC-RETICULUM

The eukaryotic elongation factor-1 (EF-1) consists of four subunits, E F-1 alpha, EF-1 beta, EF-1 gamma and EF-1 delta which induce efficient transfer of aminoacyl-tRNA to the ribosome, In this process EF-1 alph a . GTP acts as the carrier of the aminoacyl-tRNA on its way to the ri bosome, After release of aminoacyl-tRNA to the ribosome under concomit ant hydrolysis of GTP, the inactive EF-1 alpha . GDP form is recycled to EF-1 alpha . GTP by EF-1 beta gamma delta, In eukaryotic cells the concentration of EF-1 alpha exceeds that of the complex beta gamma del ta by a factor of 5-10. In order to delineate the intracellular locali zation of the different subunits of EF-1, antibodies against the EF-1 subunits have been elicited and indirect immunofluorescence microscopy experiments were performed. In human fibroblasts, the guanine nucleot ide exchange part of EF-1, EF-1 beta gamma delta, was found to co-loca lize with the endoplasmic reticulum (ER), displaying a distinct fine-s tructure in its staining pattern, The guanine nucleotide-binding subun it of EF-1, EF-1 alpha, shows a more diffuse distribution throughout t he cytoplasm and is, in addition, associated with the nucleus.