Structural Biology

Dynamics of a protein knot

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Science  14 Oct 2016:
Vol. 354, Issue 6309, pp. 193-1934
DOI: 10.1126/science.354.6309.193-f

A small fraction of proteins have an unusual conformation in which the backbone forms a knot. An example is a bacterial enzyme, TrmD, that transfers a methyl group from S-adenosyl methionine (AdoMet) to a guanine nucleotide that is conserved in many transfer RNAs (tRNAs). This methyl transfer ensures accurate protein synthesis. Christian et al. combine structural, mutagenesis, and computational studies to examine the role of the protein knot in catalysis. They show that the knot binds the AdoMet in a bent conformation oriented for methyl transfer. Despite its constrained topology, the knot undergoes complex dynamics that couple AdoMet binding to tRNA binding and facilitate catalysis.

Knotted proteins such as TrmD can undergo complex internal movements.

CREDIT: CHRISTIAN ET AL., NATURE STRUCTURAL & MOLECULAR BIOLOGY (29 AUGUST 2016) ©NATURE

Nat. Struct. Mol. Biol. 10.1038/nsmb.3282 (2016).

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