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Structural insights into the unique inhibitory mechanism of the silkworm protease inhibitor serpin18.

Guo PC, Dong Z, Zhao P, Zhang Y, He H, Tan X, Zhang W, Xia Q - Sci Rep (2015)

Bottom Line: Notably, this inhibitiory reaction results from the formation of an intermediate complex, which then follows for the digestion of protease and inhibitor into small fragments.This activity differs from previously reported modes of inhibition for serpins.Our findings have thus provided novel structural insights into the unique inhibitory mechanism of serpin18.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, 216, Tiansheng Road, Beibei, Chongqing 400716, People's Republic of China.

ABSTRACT
Serpins generally serve as inhibitors that utilize a mobile reactive center loop (RCL) as bait to trap protease targets. Here, we present the crystal structure of serpin18 from Bombyx mori at 1.65 Å resolution, which has a very short and stable RCL. Activity analysis showed that the inhibitory target of serpin18 is a cysteine protease rather than a serine protease. Notably, this inhibitiory reaction results from the formation of an intermediate complex, which then follows for the digestion of protease and inhibitor into small fragments. This activity differs from previously reported modes of inhibition for serpins. Our findings have thus provided novel structural insights into the unique inhibitory mechanism of serpin18. Furthermore, one physiological target of serpin18, fibroinase, was identified, which enables us to better define the potential role for serpin18 in regulating fibroinase activity during B. mori development.

No MeSH data available.


Related in: MedlinePlus

Close-up view of RCL.(A) Comparision of the overallstructure between serpin18 (orange) and human plasminogen activator inhibitor-1 (PDB: 1DB2, blue), (B) human plasminogen activator inhibitor-1 complexed with plasminogen activator (PDB: 3PB1, lightmagenta) and (C) Ovalbumin (PDB: 1OVA, green). All figures were prepared using PyMOL. The reactive center loop of serpin18 and the counterparts of serpins are highlight. (D) Structure-based multialignment of Bombyx mori serpin18 (NP_001139711.1) and 1DB2, Homo sapiens plasminogen activator inhibitor-1 (NP_000593.1; Identity, 18.8%; RMSD, 4.2 Å); 3PB1, Homo sapiens plasminogen activator inhibitor-1 ((NP_000593.1; Identity, 18.6%; RMSD, 4.6 Å ); 1HP7, Homo sapiens alpha-1-antitrypsin (NP_000286.3; Identity, 21.3%; RMSD, 4.5 Å) and 1OVA, Gallus gallus ovalbumin (NP_001073231.1; Identity, 16.9%; RMSD, 4.3 Å). The second structure elements are indicated under the primary sequences, and the conserved residues are shaded in blue. The multialignment was generated based on the structural superposition44.
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f2: Close-up view of RCL.(A) Comparision of the overallstructure between serpin18 (orange) and human plasminogen activator inhibitor-1 (PDB: 1DB2, blue), (B) human plasminogen activator inhibitor-1 complexed with plasminogen activator (PDB: 3PB1, lightmagenta) and (C) Ovalbumin (PDB: 1OVA, green). All figures were prepared using PyMOL. The reactive center loop of serpin18 and the counterparts of serpins are highlight. (D) Structure-based multialignment of Bombyx mori serpin18 (NP_001139711.1) and 1DB2, Homo sapiens plasminogen activator inhibitor-1 (NP_000593.1; Identity, 18.8%; RMSD, 4.2 Å); 3PB1, Homo sapiens plasminogen activator inhibitor-1 ((NP_000593.1; Identity, 18.6%; RMSD, 4.6 Å ); 1HP7, Homo sapiens alpha-1-antitrypsin (NP_000286.3; Identity, 21.3%; RMSD, 4.5 Å) and 1OVA, Gallus gallus ovalbumin (NP_001073231.1; Identity, 16.9%; RMSD, 4.3 Å). The second structure elements are indicated under the primary sequences, and the conserved residues are shaded in blue. The multialignment was generated based on the structural superposition44.

Mentions: To determine the differences between serpin18 and the other classical serpins, we superimposed serpin18 against another three structures of uncleaved serpins that had been previously deposited in the Protein Data Bank. Superposition of serpin18 against all counterparts yielded an overall root mean square deviation (RMSD) in the range of 4.2–4.6 Å over ~360 Cα atoms, implying that they adopt a distinct conformation despite sharing a similar structure topology (Fig. 2A–C). In a careful analysis of the helical region, we found that the helical region of serpin18 adopts a pattern similar to other serpins. Within the core domain, the three β-sheets in serpin18 are bent more closely towards the core of the protein compared to those of other serpins, especially β-sheet C. Notably, the counterpart of this short helix in typical serpin molecules is relaxed into a β-strand (designed sC1) in serpin18 and is bent towards the core of the molecule, leaving space for the short helix of RCL (Fig. S2).


Structural insights into the unique inhibitory mechanism of the silkworm protease inhibitor serpin18.

Guo PC, Dong Z, Zhao P, Zhang Y, He H, Tan X, Zhang W, Xia Q - Sci Rep (2015)

Close-up view of RCL.(A) Comparision of the overallstructure between serpin18 (orange) and human plasminogen activator inhibitor-1 (PDB: 1DB2, blue), (B) human plasminogen activator inhibitor-1 complexed with plasminogen activator (PDB: 3PB1, lightmagenta) and (C) Ovalbumin (PDB: 1OVA, green). All figures were prepared using PyMOL. The reactive center loop of serpin18 and the counterparts of serpins are highlight. (D) Structure-based multialignment of Bombyx mori serpin18 (NP_001139711.1) and 1DB2, Homo sapiens plasminogen activator inhibitor-1 (NP_000593.1; Identity, 18.8%; RMSD, 4.2 Å); 3PB1, Homo sapiens plasminogen activator inhibitor-1 ((NP_000593.1; Identity, 18.6%; RMSD, 4.6 Å ); 1HP7, Homo sapiens alpha-1-antitrypsin (NP_000286.3; Identity, 21.3%; RMSD, 4.5 Å) and 1OVA, Gallus gallus ovalbumin (NP_001073231.1; Identity, 16.9%; RMSD, 4.3 Å). The second structure elements are indicated under the primary sequences, and the conserved residues are shaded in blue. The multialignment was generated based on the structural superposition44.
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Related In: Results  -  Collection

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f2: Close-up view of RCL.(A) Comparision of the overallstructure between serpin18 (orange) and human plasminogen activator inhibitor-1 (PDB: 1DB2, blue), (B) human plasminogen activator inhibitor-1 complexed with plasminogen activator (PDB: 3PB1, lightmagenta) and (C) Ovalbumin (PDB: 1OVA, green). All figures were prepared using PyMOL. The reactive center loop of serpin18 and the counterparts of serpins are highlight. (D) Structure-based multialignment of Bombyx mori serpin18 (NP_001139711.1) and 1DB2, Homo sapiens plasminogen activator inhibitor-1 (NP_000593.1; Identity, 18.8%; RMSD, 4.2 Å); 3PB1, Homo sapiens plasminogen activator inhibitor-1 ((NP_000593.1; Identity, 18.6%; RMSD, 4.6 Å ); 1HP7, Homo sapiens alpha-1-antitrypsin (NP_000286.3; Identity, 21.3%; RMSD, 4.5 Å) and 1OVA, Gallus gallus ovalbumin (NP_001073231.1; Identity, 16.9%; RMSD, 4.3 Å). The second structure elements are indicated under the primary sequences, and the conserved residues are shaded in blue. The multialignment was generated based on the structural superposition44.
Mentions: To determine the differences between serpin18 and the other classical serpins, we superimposed serpin18 against another three structures of uncleaved serpins that had been previously deposited in the Protein Data Bank. Superposition of serpin18 against all counterparts yielded an overall root mean square deviation (RMSD) in the range of 4.2–4.6 Å over ~360 Cα atoms, implying that they adopt a distinct conformation despite sharing a similar structure topology (Fig. 2A–C). In a careful analysis of the helical region, we found that the helical region of serpin18 adopts a pattern similar to other serpins. Within the core domain, the three β-sheets in serpin18 are bent more closely towards the core of the protein compared to those of other serpins, especially β-sheet C. Notably, the counterpart of this short helix in typical serpin molecules is relaxed into a β-strand (designed sC1) in serpin18 and is bent towards the core of the molecule, leaving space for the short helix of RCL (Fig. S2).

Bottom Line: Notably, this inhibitiory reaction results from the formation of an intermediate complex, which then follows for the digestion of protease and inhibitor into small fragments.This activity differs from previously reported modes of inhibition for serpins.Our findings have thus provided novel structural insights into the unique inhibitory mechanism of serpin18.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, 216, Tiansheng Road, Beibei, Chongqing 400716, People's Republic of China.

ABSTRACT
Serpins generally serve as inhibitors that utilize a mobile reactive center loop (RCL) as bait to trap protease targets. Here, we present the crystal structure of serpin18 from Bombyx mori at 1.65 Å resolution, which has a very short and stable RCL. Activity analysis showed that the inhibitory target of serpin18 is a cysteine protease rather than a serine protease. Notably, this inhibitiory reaction results from the formation of an intermediate complex, which then follows for the digestion of protease and inhibitor into small fragments. This activity differs from previously reported modes of inhibition for serpins. Our findings have thus provided novel structural insights into the unique inhibitory mechanism of serpin18. Furthermore, one physiological target of serpin18, fibroinase, was identified, which enables us to better define the potential role for serpin18 in regulating fibroinase activity during B. mori development.

No MeSH data available.


Related in: MedlinePlus