PolyA+RNA from the fundal region of the fourth calf stomach of selected animals, characterized by a relatively high amount of chymosin in the mucosa, was isolated by the guanidine isocyanate method. The polyA+RNA, enriched by poly(U)sepharose 4 B chromatography and analysed by in vitro translation in a reticulocyte lysate system with 35S methionine, resulted after SDS gel electrophoresis and fluorography in a significant protein band which could he precipitated by using an appropriate antichyniosin serum. The enrichment of the specific mRNA was calculated to a value of 5%. Double-stranded cDNA was prepared from 25 pg polyA+RNA by sequential actions of reverse transcriptase, DNA polymerase-KLENOW fragment, S 1 nuclease and terminal transferase. The dC-tailed ds-cDNA has been cloned into the dG-tailed PstI-site of the linearized pBR322. Screening of 1500 recombinants was done by in situ hybridization. Specific recombinants were detected, which represent together the prochymosin sequence.We would like to thank M. WOLF and S. ICUBART Die Gene fur thermophile alpha-Amylase von Bacillus licheniform@ und fur niesophile alpha-Amylase von B . amylolipuefaciens wurden nach der ,,shot gun"-Methode in Plasmid-Vektoren kloniert, wobei B. subtiEis 168 als Wirtssystem diente. Durch Reklonierung in das StreptococcebPlasmid pDB 101 (BEHNKE et al., 1979) konnten fur beide Amylasen stabile rekomhinante Plasmide erzeugt werden. Die Reklonierung des Gens fur mesophile alpha-Amylase erfolgte nach einer neuen Variante der ,,shot gun"-Methode,
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