Losartan/Simvastatin

Partially and fully reconstituted complexes of the 5 S RNA and two 5 s RNA binding proteins (HL13 and HL19) from H. cutirubrum were examined using ethidium bromide binding, CD spectra, and limited nuclease digestion.The binding of 5 S RNA to HL13 was studied by means of the quenching of tryptophan fluorescence; a value of 10⁸M^-1 was estimated for the association constant in 3.7M KCl.A study of the CD spectra in the 200 to 240-nm region also indicated that this protein underwent some conformational change when bound.The addition of HL13 chased ethidium bromide bound to the 5 S RNA.The only effect observed on binding HL19 was an enhanced association constant for HL13 as inferred from a change in shape of the ethidium bromide chasing curve.Addition of HL13 also gave rise to a partial protection of the 5 S RNA against T₁ RNase digestion; in contrast, it brought about an enhanced susceptibility to pancreatic RNase digestion.Addition of HL19 had no effect in either case.Thus, protein HL13 alone is responsible for the corresponding CD and nuclease digestion observations on the native H. cutirubrum 5 S RNA-protein complex and 5 S RNA previously reported.Furthermore, despite the limited sequence homol., there is a marked structural homol., within their resp. 5 S RNA complexes, between protein HL13 from H. cutirubrum and protein EL18 from Escherichia coli.Similarly, HL19 appears to have a similar role as EL5 in the E. coli complex.