Properties of Native and Nicked Elongation Factor Tu from Thermus thermophilus HB 8

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Abstract
Two alternative procedures for the isolation of the elongation factor Tu from Thermus thermophilus were compared and the properties of a specifically nicked EF‐Tu · GDP were examined in detail. Although the native elongation factor possessed similar catalytic activities in all reactions investigated as the protein isolated by Arai et al. [Eur. J. Biochem. 92, 509–519 and 521–531 (1978)] it could not be crystallized. The nicked EF‐Tu, consisting of two associated fragments with molecular weights of 41000 and 8000 respectively, was active in binding GDP, GTP and in the formation of Phe‐tRNAPhe. EF‐Tu · GTP ternary complex. However, it did not promote poly(U)‐dependent synthesis of polyphenylalanine on Escherichia coli ribosomes. The isolated fragment of a molecular weight of about 41 000 did not bind GDP. This activity could be reconstituted with the supplement of the small 8000‐M, fragment. It is demonstrated that, in contrast to the native EF‐Tu, the nicked EF‐Tu forms high‐molecular‐weight aggregates. Cleavage of the polypeptide chain of EF‐Tu from T. therrnoplzilus stimulates the crystallization of this protein.

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