Requirements for the inactivation of ribosomes by gelonin

Abstract

Inactivation of Artemia salina and rabbit ribosomes by gelonin requires ATP and a high-Mr factor present in the rabbit reticulocyte-lysate post-ribosomal supernatant. The kinetic constants of the gelonin-catalysed release of adenine from A. salina ribosomes are Km = 4.35 microM and Kcat. = 0.1 min-1 in the absence of cofactors, and Km = 1.15 microM and Kcat. = 108 min-1 in their presence. The last two values are similar to those measured for ricin A chain in the absence of cofactors (Km = 2.02 microM and Kcat. = 317 min-1).