Abstract
The polyamines occur in essentially all biological systems [ 1,2]. Although the significance of polyamines in physiological and biochemical processes is recognized, their precise role in living systems is only beginning to be understood. Because of their cationic nature polyamines bind strongly to nucleic acids, the binding being considerably reduced by Mg2+ and Na+ [3]. Most remarkable is the stabilization of a tertiary structure of transfer RNA by spermine: the best crystals of transfer RNA grow in the presence of spermine [4]. The polyamines affect the biosynthesis, maturation and stability of ribosomes [5] and stimulate the translation of natural and synthetic mRNAs [6-91. Spermidine increases the fidelity of poly(U) translation in Escherichiu coli [8] and wheat germ [9] systems. The rate of many processes involving tRNA is significantly enhanced by polyamines: methylation [IO], aminoacylation [I 11, and incorporation of 3’-terminal nucleotides into tRNA [ 121. This effects can be explained as modification of the tRNA reactivity after direct polyamine binding [2,13,14]; however, the polyamine binding to an enzyme can not be excluded. For example, it has been shown, using fluorimetric titration, that spermine binds to an effector site of isoleucyl-tRNA synthetase with Kd 0.25 mM [15], but the significance of this binding in tRNA aminoacylation has not been elucidated. In another study of spermineprotein interaction it has been shown that the polyamine binds to an uridine-specific ribonuclease and changes the specificity of the enzyme [ 161. The effects of polyamines on processes involving DNA are also well documented [ 17-201. I have shown the role for protein-protein inter-
Published Version
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