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A conserved mechanism of autoinhibition for the AMPK kinase domain: ATP-binding site and catalytic loop refolding as a means of regulation.

ABSTRACT: The AMP-activated protein kinase (AMPK) is a highly conserved trimeric protein complex that is responsible for energy homeostasis in eukaryotic cells. Here, a 1.9 A resolution crystal structure of the isolated kinase domain from the alpha2 subunit of human AMPK, the first from a multicellular organism, is presented. This human form adopts a catalytically inactive state with distorted ATP-binding and substrate-binding sites. The ATP site is affected by changes in the base of the activation loop, which has moved into an inhibited DFG-out conformation. The substrate-binding site is disturbed by changes within the AMPKalpha2 catalytic loop that further distort the enzyme from a catalytically active form. Similar structural rearrangements have been observed in a yeast AMPK homologue in response to the binding of its auto-inhibitory domain; restructuring of the kinase catalytic loop is therefore a conserved feature of the AMPK protein family and is likely to represent an inhibitory mechanism that is utilized during function.

SUBMITTER: Littler DR

PROVIDER: S-EPMC2815679 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature

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A conserved mechanism of autoinhibition for the AMPK kinase domain: ATP-binding site and catalytic loop refolding as a means of regulation.

Littler Dene R DR Walker John R JR Davis Tara T Wybenga-Groot Leanne E LE Finerty Patrick J PJ Newman Elena E Mackenzie Farell F Dhe-Paganon Sirano S

Acta crystallographica. Section F, Structural biology and crystallization communications 20100127 Pt 2

The AMP-activated protein kinase (AMPK) is a highly conserved trimeric protein complex that is responsible for energy homeostasis in eukaryotic cells. Here, a 1.9 A resolution crystal structure of the isolated kinase domain from the alpha2 subunit of human AMPK, the first from a multicellular organism, is presented. This human form adopts a catalytically inactive state with distorted ATP-binding and substrate-binding sites. The ATP site is affected by changes in the base of the activation loop, ...[more]

PMID: 20124709

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Project description:BACKGROUND: The Aim of this study is to study the minimum zinc dependent metalloprotease catalytic folding motif, helix B Met loop-helix C, with proteolytic catalytic activities in metzincin super family. The metzincin super family share a catalytic domain consisting of a twisted five-stranded ? sheet and three long ? helices (A, B and C). The catalytic zinc is at the bottom of the cleft and is ligated by three His residues in the consensus sequence motif, HEXXHXXGXXH, which is located in helix B and part of the adjacent Met turn region. An interesting question is - what is the minimum portion of the enzyme that still possesses catalytic and inhibitor recognition?" METHODS: We have expressed a 60-residue truncated form of matrilysin which retains only the helix B-Met turn-helix C region and deletes helix A and the five-stranded ? sheet which form the upper portion of the active cleft. This is only 1/4 of the full catalytic domain. The E. coli derived 6 kDa MMP-7 ZBD fragments were purified and refolded. The proteolytic activities were analyzed by Mca-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2 peptide assay and CM-transferrin zymography analysis. SC44463, BB94 and Phosphoramidon were computationally docked into the 3 day structure of the human MMP7 ZBD and TAD and thermolysin using the docking program GOLD. RESULTS: This minimal 6 kDa matrilysin has been refolded and shown to have proteolytic activity in the Mca-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2 peptide assay. Triton X-100 and heparin are important factors in the refolding environment for this mini-enzyme matrilysin. This minienzyme has the proteolytic activity towards peptide substrate, but the hexamer and octamer of the mini MMP-7 complex demonstrates the CM-transferrin proteolytic activities in zymographic analysis. Peptide digestion is inhibited by SC44463, specific MMP7 inhibitors, but not phosphorimadon. Interestingly, the mini MMP-7 can be processed by autolysis and producing ~ 6 ~ 7 kDa fragments. Thus, many of the functions of the enzyme are retained indicating that the helix B-Met loop-helix C is the minimal functional "domain" found to date for the matrixin family. CONCLUSIONS: The helix B-Met loop-helix C folding conserved in metalloprotease metzincin super family is able to facilitate proteolytic catalysis for specific substrate and inhibitor recognition. The autolysis processing and producing 6 kDa mini MMP-7 is the smallest metalloprotease in living world.

Dataset Information

A conserved mechanism of autoinhibition for the AMPK kinase domain: ATP-binding site and catalytic loop refolding as a means of regulation.

Publications

A conserved mechanism of autoinhibition for the AMPK kinase domain: ATP-binding site and catalytic loop refolding as a means of regulation.

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