Abstract
BACKGROUND AND AIMS: Pathogenesis-Related 1 (PR-1) proteins are small secreted proteins that typically accumulate upon pathogen attack and serve as hallmarks of plant immune activation. Despite their widespread use as defence markers, their biochemical properties and native structural features remain largely unresolved. This study aimed to isolate, characterize and determine the crystal structure of a native PR-1 protein (MsPR-1b) that predominates in the floral nectar of Mucuna sempervirens, a woody leguminous vine, to provide insight into the molecular diversity and possible functional specialization of PR-1 proteins. METHODS: MsPR-1b was purified from raw nectar using ion-exchange and size-exclusion chromatography. The purified protein was analysed for molecular mass and glycosylation status, and its three-dimensional structure was determined by X-ray crystallography at 2.0 Å resolution. The full-length complementary DNA sequence was obtained through 3' and 5' rapid amplification of complementary DNA ends PCR, and tissue-specific expression was examined by quantitative PCR. Lipid-binding ability and antimicrobial activity were assessed by fluorescence spectroscopy and the disc diffusion method, respectively. KEY RESULTS: The MsPR-1b gene encodes a 164-amino-acid precursor containing an N-terminal signal peptide. Expression was detected predominantly in the nectary. The mature MsPR-1b is a small basic secreted protein (15 134 Da, pI 9.4) that lacks glycosylation. The crystal structure, representing the first native PR-1 protein purified from its natural source, revealed a homodimer. Each monomer adopts the conserved α-β-α sandwich fold characteristic of the CAP superfamily and contains two intrachain disulphide bonds. MsPR-1b displays no detectable lipid-binding capacity or direct antimicrobial activity. CONCLUSIONS: MsPR-1b provides the first structural view of a native plant PR-1 protein and indicates that nectar-secreted PR-1s might perform specialized, non-defensive functions distinct from canonical pathogen-related roles.
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Claims 10
Claim · model-written summary
The MsPR-1b gene of Mucuna sempervirens encodes a 164-amino-acid precursor with an N-terminal signal peptide.
- Taxon
- Mucuna sempervirens
.jpg?width=60)
Mucuna sempervirenst0 - Gene
- MsPR-1b genee1
- Outcome
- 164-amino-acid precursor containing an N-terminal signal peptidee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
t0“Mucuna sempervirens”
e1“The MsPR-1b gene encodes a 164-amino-acid precursor containing an N-terminal signal peptide”
Claim · model-written summary
MsPR-1b expression in Mucuna sempervirens was detected predominantly in the nectary.
- Taxon
- Mucuna sempervirensMucuna sempervirenst0
- Organ / stage
- nectarye1
- Outcome
- Expression was detected predominantlye1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Mucuna sempervirens”
e1“Expression was detected predominantly in the nectary”
Claim · model-written summary
The mature MsPR-1b is a small basic secreted protein of 15 134 Da.
- Taxon
- Mucuna sempervirensMucuna sempervirenst0
- Gene
- MsPR-1be1
- Outcome
- small basic secreted proteine1
- Value
- 15 134 Dae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Mucuna sempervirens”
e1“The mature MsPR-1b is a small basic secreted protein (15 134 Da, pI 9.4) that lacks glycosylation”
Claim · model-written summary
The mature MsPR-1b has a pI of 9.4.
- Taxon
- Mucuna sempervirensMucuna sempervirenst0
- Gene
- MsPR-1be1
- Outcome
- pIe1
- Value
- 9.4e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Mucuna sempervirens”
e1“The mature MsPR-1b is a small basic secreted protein (15 134 Da, pI 9.4) that lacks glycosylation”
Claim · model-written summary
The mature MsPR-1b lacks glycosylation.
- Taxon
- Mucuna sempervirensMucuna sempervirenst0
- Gene
- MsPR-1be1
- Outcome
- lacks glycosylatione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Mucuna sempervirens”
e1“The mature MsPR-1b is a small basic secreted protein (15 134 Da, pI 9.4) that lacks glycosylation”
Claim · model-written summary
The crystal structure of native MsPR-1b, the first native PR-1 protein purified from its natural source, revealed a homodimer.
- Taxon
- Mucuna sempervirensMucuna sempervirenst0
- Outcome
- homodimere1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Mucuna sempervirens”
e1“The crystal structure, representing the first native PR-1 protein purified from its natural source, revealed a homodimer”
Claim · model-written summary
Each MsPR-1b monomer adopts the conserved α-β-α sandwich fold characteristic of the CAP superfamily.
- Taxon
- Mucuna sempervirensMucuna sempervirenst0
- Outcome
- conserved α-β-α sandwich folde1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Mucuna sempervirens”
e1“Each monomer adopts the conserved α-β-α sandwich fold characteristic of the CAP superfamily”
Claim · model-written summary
Each MsPR-1b monomer contains two intrachain disulphide bonds.
- Taxon
- Mucuna sempervirensMucuna sempervirenst0
- Outcome
- two intrachain disulphide bondse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Mucuna sempervirens”
e1“Each monomer adopts the conserved α-β-α sandwich fold characteristic of the CAP superfamily and contains two intrachain disulphide bonds”
Claim · model-written summary
MsPR-1b displayed no detectable lipid-binding capacity or direct antimicrobial activity.
- Taxon
- Mucuna sempervirensMucuna sempervirenst0
- Gene
- MsPR-1be1
- Outcome
- lipid-binding capacity or direct antimicrobial activitye1
- Direction
- no detectablee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Mucuna sempervirens”
e1“MsPR-1b displays no detectable lipid-binding capacity or direct antimicrobial activity”
Claim · model-written summary
The authors suggest that nectar-secreted PR-1s might perform specialized, non-defensive functions distinct from canonical pathogen-related roles.
- Taxon
- Mucuna sempervirensMucuna sempervirenst0
- Outcome
- specialized, non-defensive functionse1
- Qualifier
- might performe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Mucuna sempervirens”
e1“nectar-secreted PR-1s might perform specialized, non-defensive functions distinct from canonical pathogen-related roles”