Passage of radioactive amino acids through nonprotein fractions of hen oviduct during incorporation into protein.
نویسنده
چکیده
The hen oviduct has been observed to lose virtually all its ability to incorporate free ammo acid into protein upon homogenation (2). In many instances, however, homogenation of a prelabeled mince, followed by removal of most of the radioactivity, and subsequent incubation, has led to a larger quantity of radioactivity contained in the protein fraction than was present at the start or early in the incubation. Although this phenomenon is not always observed, it has been observed frequently with radioactive alanine (3), phenylalanine, and valine (see Fig. 1 and Table I). The observation has been interpreted as an indication of the existence of an intermediate stage, between free amino acid and protein, which cannot be formed in the homogenate, but once formed in the intact cell preparation serves as a source of radioactivity for the protein. If such a precursor substance does exist, it would have to obey certain relationships in the process of amino acid incorporation. In the incubation of prelabeled homogenate, the radioactivity of the precursor material should decrease as that of the protein increases, since free amino acid would not replenish its pool. This precursor material should become labeled very quickly compared to the protein, should have a rapid turnover with respect to its bound amino acids, and should contain a wide spectrum of the amino acids required for protein synthesis. With the above considerations in mind, all of the material of the hen oviduct system was examined in the following fractions: cold trichloroacetic acid soluble, hot trichloroacetic acid soluble, organic solvent soluble, and proteins. The results suggest that the fraction most closely fitting the necessary criteria is the organic solvent soluble fraction (lipides).
منابع مشابه
Incorporation of amino acids into lipoidal material by microsomal and supernatant fractions of rat tissues.
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عنوان ژورنال:
- The Journal of biological chemistry
دوره 234 6 شماره
صفحات -
تاریخ انتشار 1959