VALYL-TRANSFER-RNA SYNTHETASE FROM ARTEMIA - PURIFICATION AND ASSOCIATION WITH ELONGATION-FACTOR

Two components of the protein biosynthetic machinery, valyl-transfer R NA synthetase (VRS) and elongation factor 1 (EF-1), have been isolated as a complex from several mammalian tissues. However, yeast VRS, whic h lacks an amino-terminal extension, does not associate with EF-1. We purified VRS from the brine shrimp Artemia and investigated its intera ction with EF-1. Western blotting of crude Artemia extracts revealed t he presence of two forms of VRS, differing in size and capacity to ass ociate with EF-1. About 80% of the total VRS corresponds to a polypept ide of 130 kDa which behaves as a monomer upon gel filtration. Only th e larger form of 140 kDa coelutes, cosediments and co-immunoprecipitat es with the EF-1 alpha(2) beta gamma delta complex. The ratio of the t wo forms of VRS remains constant throughout early development. The pos sible origin and mode of expression of the two forms of VRS present in Artemia are discussed.