Amphibian egg jelly coat and fertilization envelope: Involvement in sodium-dependent amino acid transport

Abstract

1. 1. Amino acid transport by Xenopus laevis stage 23, 24 embryos requires the jelly coat and fertilization envelope (JCFE) for mostly Na +-dependent amino acid transport but not for mostly Na +-independent amino acid transport. 2. 2. The direct involvement of JCFE in Na +-dependent transport was shown by reconstituting dejellied (i.e. JCFE removal) embryos with the removed JCFE to restore Na +-dependent transport. This restoration of activity also occurred when the JCFE were homogenized, showing that components of the JCFE were actively participating in the transport process. Dialysis of the JCFE showed the active components were neither soluble nor dialyzable since full activity was retained by the dialyzed JCFE but not in the dialyzate supernatant or dialysis medium. 3. 3. The enhancement of activity could be restored partly with increased levels of Na +, suggesting the JCFE components may be involved in the Na + effect itself. 4. 4. JCFE which were frozen-thawed, heated to 55°C for 10 min, or sonicated for 1–3 min were unable to restore the amino acid transport levels to those seen in controls, as were JCFE solubilized with dithiothreitol or guanidinium hydrochloride. 5. 5. No ATPase activity nor specific alanine- or Na + -binding was detected in intact JCFE. 6. 6. A definite relationship between presence of JCFE and glycine transport was evident in stoichiometric studies.