HutP_Bacsu

HutP regulates the expression of the hut structural genes of Bacillus subtilis by an anti-termination mechanism and requires two components, Mg2+ ions and L-histidine. HutP recognizes three UAG triplet units, separated by four non-conserved nucleotides on the terminator region. Here we report the 1.60-A resolution crystal structure of the quaternary complex (HutP-L-histidine-Mg2+-21-base single-stranded RNA). In the complex, the RNA adopts a novel triangular fold on the hexameric surface of HutP, without any base-pairing, and binds to the protein mostly by specific protein-base interactions. The structure explains how the HutP and RNA interactions are regulated critically by the l-histidine and Mg2+ ion through the structural rearrangement. To gain insights into these structural rearrangements, we solved two additional crystal structures (uncomplexed HutP and HutP-L-histidine-Mg2+) that revealed the intermediate structures of HutP (before forming an active structure) and the importance of the Mg2+ ion interactions in the complexes.

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Some information

Protein chains

Fasta-format

>sp|P10943|HUTP_BACSU Hut operon positive regulatory protein OS=Bacillus subtilis GN=hutP PE=1 SV=4 MTLHKERRIGRLSVLLLLNEAEESTQVEELERDGWKVCLGKVGSMDAHKVVAAIETASKK SGVIQSEGYRESHALYHATMEALHGVTRGEMLLGSLLRTVGLRFAVLRGNPYESEAEGDW IAVSLYGTIGAPIKGLEHETFGVGINHI

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Complex formation

Electrostatic surface potential models of HutP and the proposed mechanism for the anti-terminator complex formation.

a-d) Molecular surfaces of the HutP dimer of uncomplexed HutP (a), HutP -HBN (b), the HutP -l-histidine -Mg2+ complex (c) and the quaternary HutP complex (d), coloured in accordance with the electrostatic potential. HBN, l-histidine and RNA are represented by ball-and-stick models. Mg2+ ions are represented by a cpk model;

e) a schematic model proposed for HutP anti-terminator complex formation;

f) a proposed model for the existence of two potential binding sites (highlighted in blue boxes) within the terminator region.

The GC-rich region is highlighted in the red box. The RNA-binding residues are indicated by magenta and green.