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The Gordian Knot is a legend associated with Alexander the Great. It is often used as a metaphor for an intractable problem, solved by a bold stroke ("cutting the Gordian knot"). Here the knot represents structural motifs in messenger RNA that pose a roadblock to scanning ribosomes and impede translation. Studies from the Boris–Lawrie group demonstrate that RNA helicase A recognizes the highly structured 5' untranslated region in selected messenger RNAs and stimulates efficient translation. p 509
Since the discovery of Prp16, a spliceosomal ATPase that alters the fidelity of splicing, many other ATPases associated with the spliceosome have been postulated to work similarly. The finding that Prp22, a DEAH-box ATPase, functions as a fidelity factor for the second step of splicing supports this hypothesis.
The E2 enzymes for ubiquitin and SUMO conjugation share a conserved active site that has long been mysterious for lack of identifiable catalytic residues. In an elegant tour de force, it is now shown how three E2 residues not only position the target lysine but also substantially lower its pK to allow deprotonation and efficient substrate transfer.
A recent report identifies a cellular protein that recognizes inner nuclear membrane (INM) targeting signals. This finding provides the missing link for the transport of large inner nuclear membrane proteins as they travel from the cytosolic face of the endoplasmic reticulum to the INM.
The crystal structure of the full-length yeast Hsp90 sheds new light on the conformational cycle and the functional regulation of this important molecular chaperone.