Visualizing transient events in amino-terminal autoprocessing of HIV-1 protease

Article

关键词: ENCOUNTER COMPLEXES;    NMR;    BINDING;    KINETICS;    ENHANCEMENT;    PRECURSOR;    DYNAMICS;    CLEAVAGE;    ASSOCIATION;    INHIBITORS;   

DOI  :  10.1038/nature07342

来源: SCIE

【 摘 要 】

HIV- 1 protease processes the Gag and Gag- Pol polyproteins into mature structural and functional proteins, including itself, and is therefore indispensable for viral maturation(1,2). The mature protease is active only as a dimer(3-5) with each subunit contributing catalytic residues(6). The full- length transframe region protease precursor appears to be monomeric yet undergoes maturation via intramolecular cleavage of a putative precursor dimer(5,7-11), concomitant with the appearance of mature- like catalytic activity(7,9). How such intramolecular cleavage can occur when the amino and carboxy termini of the mature protease are part of an intersubunit beta-sheet located distal from the active site is unclear. Here we visualize the early events in N- terminal autoprocessing using an inactive mini- precursor with a four- residue N- terminal extension that mimics the transframe region protease precursor(5,12). Using paramagnetic relaxation enhancement, a technique that is exquisitely sensitive to the presence of minor species(13-16), we show that the mini- precursor forms highly transient, lowly populated (3-5%) dimeric encounter complexes that involve the mature dimer interface but occupy a wide range of subunit orientations relative to the mature dimer. Furthermore, the occupancy of the mature dimer configuration constitutes a very small fraction of the self- associated species ( accounting for the very low enzymatic activity of the protease precursor), and the N- terminal extension makes transient intra- and intersubunit contacts with the substrate binding site and is therefore available for autocleavage when the correct dimer orientation is sampled within the encounter complex ensemble.

【 授权许可】

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