A Dimeric Structure for Archaeal Box C/D Small Ribonucleoproteins

A particular set of ubiquitous small (nucleolar) ribonucleoproteins are important for optimal ribosome function and protein synthesis. Bleichert et al. (p. [1384][1]) used electron microscopy and single-particle analysis to investigate the structure of an archaeal version that contains the small RNA (sRNA) and all the associated core proteins. Unexpectedly, this ribonucleoprotein is a homodimer, formed of two sRNAs and four copies of each of the core proteins. This dimer is likely to be the enzymatically active form, as mutations disrupting di-sRNP formation inhibited activity. [1]: /lookup/doi/10.1126/science.1176099