title: SaRD, a new protein isolated from the extremophile archaeon Sulfolobus acidocaldarius, is a thermostable ribonuclease with DNA-binding properties.
abstract: We have isolated the thermostable 9 kDa SaRD-protein from Sulfolobus acidocaldarius which exhibit RNase activity as well as DNA-binding properties (SaRD). The amino acid composition and the sequence of the 16 N-terminal amino acids show similarities to different RNases as well as to DNA-binding proteins from thermophilic archea. The RNase activity was demonstrated by 5S rRNA degradation, thin layer chromatography and a zymogram. The temperature optimum for the RNase activity is 65 degrees C. The pH optimum ranges from 6.5-7.0. DNA-binding properties were shown by gel-shift assays on agarose gels. In a similar way SaRD mediated protection of DNA against DNase I digestion and Sau3A I restriction could be demonstrated. The melting point (Tm) of genomic DNA was raised from 68 degrees C to 90 degrees C by addition of the SaRD-protein. CD spectroscopy indicated that SaRD is very stable near neutral pH and can neither be unfolded by temperatures up to 85% C nor by addition of 8 M urea.
authors.affiliation: Institut für Biochemie, Medizinische Universität zu Lübeck, FRG.
authors.forename: D
authors.initials: D
authors.lastname: Kulms
authors.forename: G
authors.initials: G
authors.lastname: Schäfer
authors.forename: U
authors.initials: U
authors.lastname: Hahn
mesh_terms: D000596:Amino Acids / Q000032:analysis; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D006358:Hot Temperature; D007700:Kinetics; D008970:Molecular Weight; D011489:Protein Denaturation; D017510:Protein Folding; D012329:RNA, Bacterial / Q000378:metabolism; D012341:RNA, Ribosomal, 5S / Q000378:metabolism; D012260:Ribonucleases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D016945:Sulfolobus acidocaldarius / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D004268:DNA-Binding Proteins; D012329:RNA, Bacterial; D012341:RNA, Ribosomal, 5S; D012260:Ribonucleases