The 5‐S RNA · Protein Complex from an Extreme Halophile, Halobacterium cutirubrum

Abstract

A 5-S RNA.cntdot.protein complex was isolated from the 50-S ribosomal subunit of an extreme halophile, H. cutirubrum. The 50-S ribosomal subunit from the extreme halophile requires 3.4 M K+ and 100 mM Mg2+ for stability. If the high K+ concentration is maintained but the Mg2+ concentration lowered to 0.3 mM, the 5-S RNA.cntdot.protein complex is selectively extracted from the subunit. After being purified on an Agarose 0.5 m column the complex had a MW of about 80,000 and contained 5-S RNA and 2 proteins. HL13 and HL19, with MW (by sedimentation equilibrium) of 18,700 and 18,000, respectively. No ATPase or GTPase activity could be detected in the 5-S RNA.cntdot.protein complex. The amino acid composition and electrophoretic mobility on polyacrylamide gels indicated both proteins were much more acidic than the equivalent from Escherichia coli or Bacillus stearothermophilus. Partial amino acid sequence data suggest HL13 is homologous to EL18 and HL19 to EL5.