Crystal Structure of the Serine Protease Domain of Prophenoloxidase Activating Factor-I

Piao, Shunfu; Kim, Seul-Ki; Kim, Jung Hyun; Park, Ji Won; Lee, Bok Leul; Ha, Nam‐Chul

doi:10.1074/jbc.m611556200

Cited by 25 publications

(28 citation statements)

References 30 publications

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“…The structures of the SP domain of PPAF-I [11] and the whole PPAF-II from Holotrichia diomphalia [12] reveal a chymotrypsin-like fold of their proteinase domains (Fig. 2).…”

Section: Introductionmentioning

confidence: 99%

The expanding diversity of serine hydrolases

Botos

Wlodawer

2007

Current Opinion in Structural Biology

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SummarySerine hydrolases use a hydroxyl of a serine, assisted by one or more other residues, to cleave peptide bonds. They belong to several different families whose general mechanism is well known. However, the subtle structural differences that have recently been observed across a variety of families shed light on their functional diversity, including variations in mechanism of action, differences in the modes of substrate binding, and substrate-assisted orientation of catalytic residues. Of particular interest are the rhomboid family serine proteinases that are active within the plasma membrane, for which several new structures have been reported. Because these enzymes are involved in biological and pathological processes, many are becoming important targets of drug design.

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“…The structures of the SP domain of PPAF-I [11] and the whole PPAF-II from Holotrichia diomphalia [12] reveal a chymotrypsin-like fold of their proteinase domains (Fig. 2).…”

Section: Introductionmentioning

confidence: 99%

The expanding diversity of serine hydrolases

Botos

Wlodawer

2007

Current Opinion in Structural Biology

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“…We reported the detailed characterization of three PPAFs purified from the larvae of a large beetle, Holotrichia diomphalia (26). Two of these PPAFs have been crystallized, and these structural studies have provided details about the activation mechanism (15,16). For example, they showed that proPO cleavage alone is insufficient to produce active PO.…”

mentioning

confidence: 99%

“…Upon injury or infection, proPO in the blood plasma is activated to phenoloxidase (PO) by clip-domain serine proteases, which are called proPO-activating factors (PPAFs) or enzymes (PPAEs), or alternatively proPO-activating proteins (11)(12)(13)(14). We recently determined the crystal structures of two PPAFs and the functional roles of the clip domains during the proPO activation cascade (15,16). PO, the active form of proPO, catalyzes the production of quinones, which can nonspecifically cross-link neighboring molecules to form melanin at the injury site or all over the surface of invading microorganisms (17,18).…”

mentioning

confidence: 99%

Molecular Control of Phenoloxidase-induced Melanin Synthesis in an Insect

Kan

Kim²,

Kwon³

et al. 2008

Journal of Biological Chemistry

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The melanization reaction induced by activated phenoloxidase in arthropods must be tightly controlled because of excessive formation of quinones and excessive systemic melanization damage to the hosts. However, the molecular mechanism by which phenoloxidase-induced melanin synthesis is regulated in vivo is largely unknown. It is known that the Spätzle-processing enzyme is a key enzyme in the production of cleaved Spätzle from pro-Spätzle in the Drosophila Toll pathway. Here, we provide biochemical evidence that the Tenebrio molitor Spätzle-processing enzyme converts both the 79-kDa Tenebrio prophenoloxidase and Tenebrio clip-domain SPH1 zymogen to an active melanization complex. This complex, consisting of the 76-kDa Tenebrio phenoloxidase and an active form of Tenebrio clip-domain SPH1, efficiently produces melanin on the surface of bacteria, and this activity has a strong bactericidal effect. Interestingly, we found the phenoloxidase-induced melanization reaction to be tightly regulated by Tenebrio prophenoloxidase, which functions as a competitive inhibitor of melanization complex formation. These results demonstrate that the Tenebrio Toll pathway and the melanization reaction share a common serine protease for the regulation of these two major innate immune responses.

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“…Intrinsic Affinities of SPE to SPN48-The Clip domains of some serine proteases of insects have been implicated in the involvement of the specific activation of the clip domain-mediated proteolytic cascades, such as Toll signaling and melanin-synthesis pathways (16,17). To gain a clue of the role of the clip domain of SPE in the inhibition by SPN48, the clip domain and the serine protease domain of SPE were separately expressed as GST fusion proteins, and GST pulldown experiments were then performed.…”

Section: Spn48 Ismentioning

confidence: 99%

Structural and Functional Characterization of a Highly Specific Serpin in the Insect Innate Immunity

Jiang

Piao

Zhang

et al. 2011

Journal of Biological Chemistry

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The Toll signaling pathway, an essential innate immune response in invertebrates, is mediated via the serine protease cascade. Once activated, the serine proteases are irreversibly inactivated by serine protease inhibitors (serpins). Recently, we identified three serpin-serine protease pairs that are directly involved in the regulation of Toll signaling cascade in a large beetle, Tenebrio molitor. Of these, the serpin SPN48 was cleaved by its target serine protease, Spätzle-processing enzyme, at a noncanonical P1 residue of the serpin's reactive center loop. To address this unique cleavage, we report the crystal structure of SPN48, revealing that SPN48 exhibits a native conformation of human antithrombin, where the reactive center loop is partially inserted into the center of the largest ␤-sheet of SPN48. The crystal structure also shows that SPN48 has a putative heparin-binding site that is distinct from those of the mammalian serpins. Ensuing biochemical studies demonstrate that heparin accelerates the inhibition of Spätzle-processing enzyme by a proximity effect in targeting the SPN48. Our finding provides the molecular mechanism of how serpins tightly regulate innate immune responses in invertebrates.

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Crystal Structure of the Serine Protease Domain of Prophenoloxidase Activating Factor-I

Cited by 25 publications

References 30 publications

The expanding diversity of serine hydrolases

The expanding diversity of serine hydrolases

Molecular Control of Phenoloxidase-induced Melanin Synthesis in an Insect

Structural and Functional Characterization of a Highly Specific Serpin in the Insect Innate Immunity

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