The structure of the Escherichia coli ribonuclease P (RNase P) holoenzyme was investigated by site-directed attachment of an aryl azide crosslink reagent to specific sites in the protein subunit of the enzyme. The sites of crosslinking to the RNase P RNA subunit were mapped by primer extension to several conserved residues and structural features throughout the RNA. The results suggest rearrang...

The genes encoding the RNA subunit of ribonuclease P from the unicellular cyanobacterium Synechocystis sp. PCC 6803, and from the heterocyst-forming strains Anabaena sp. PCC 7120 and Calothrix sp. PCC 7601 were cloned using the homologous gene from Anacystis nidulans (Synechococcus sp. PCC 6301) as a probe. The genes and the flanking regions were sequenced. The genes from Anabaena and Calothrix...

A space $Y$ is called an {em extension} of a space $X$, if $Y$ contains $X$ as a dense subspace. Two extensions of $X$ are said to be {em equivalent}, if there is a homeomorphism between them which fixes $X$ point-wise. For two (equivalence classes of) extensions $Y$ and $Y'$ of $X$ let $Yleq Y'$, if there is a continuous function of $Y'$ into $Y$ which fixes $X$ point-wise. An extension $Y$ ...