Open AccessGTP Degradation to Guanine Catalyzed by Ribosomal Subunits and Microsomal‐Wash Factors
Author(s) -
GRUMMT Friedrich,
SPECKBACHER Monika
Publication year - 1975
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1975.tb02333.x
Subject(s) - gtp' , ribosome , aminoacyl trna , puromycin , guanosine , guanine , biochemistry , ribosomal rna , guanosine triphosphate , cycloheximide , hydrolysis , chemistry , transfer rna , protein biosynthesis , biology , nucleotide , enzyme , rna , gene
Ribosomes from stringent strains of bacteria generate (p)ppGpp if incubated with uncharged tRNA, a ribosomal wash fraction, GTP and ATP. By contrast, an analogous system from rat liver does not transform GTP to (p)ppGpp but degrades it to guanine. The reaction requires the ribosomal subunits, a 40000‐ M r and a 60000‐ M r microsomal wash protein factor and is inhibited if the ribosomal A‐site is charged with aminoacyl tRNA. The degradation of GTP to guanine occurs in the following four distinct reaction steps: (a) hydrolysis of GTP to GDP + P i , (b) hydrolysis of GDP to GMP + P i , (c) hydrolysis of GMP to guanosine + P i , (d) hydrolysis of guanosine to guanine + ribose. The reaction step (a) is inhibited by fusidic acid, cycloheximide, emetine, tetracycline and puromycin. The hydrolysis of GDP is inhibited strongly by fusidic acid, emetine and tetracycline. A putative physiological significance of this ribosome‐dependent pathway in the processes of growth control of animal cells under conditions of amino acid deprivation is discussed.