1P8B

SOLUTION STRUCTURE OF PA1B, A 37-AMINO ACID INSECTICIDAL PROTEIN EXTRACTED FROM PEA SEEDS (PISUM SATIVUM)

Summary for 1P8B

• Entry DOI: 10.2210/pdb1p8b/pdb
• Descriptor: Pea Albumin 1, subunit b (1 entity in total)
• Functional Keywords: inhibitor cystine-knot, plant protein
• Biological source: Pisum sativum (pea)
• Total number of polymer chains: 1
• Total formula weight: 3749.39

Authors

Jouvensal, L.,Quillien, L.,Ferrasson, E.,Rahbe, Y.,Gueguen, J.,Vovelle, F. (deposition date: 2003-05-06, release date: 2003-11-25, Last modification date: 2024-10-30)

Primary citation

Jouvensal, L.,Quillien, L.,Ferrasson, E.,Rahbe, Y.,Gueguen, J.,Vovelle, F.
PA1b, an insecticidal protein extracted from pea seeds (Pisum sativum): 1H-2-D NMR study and molecular modeling
Biochemistry, 42:11915-11923, 2003

PubMed Abstract: PA1b (pea albumin 1, subunit b) is a 37-amino acid cysteine-rich plant defense protein isolated from pea seeds (Pisum sativum). It induces short-term mortality in several pests, among which the cereal weevils Sitophilus sp. (Sitophilus oryzae, Sitophilus granarius, and Sitophilus zeamais) that are a major nuisance for stored cereals, all over the world. As such, PA1b is the first genuine protein phytotoxin specifically toxic to insects, which makes it a promising tool for seed weevil damage control. We have determined the 3-D solution structure of PA1b, using 2-D homonuclear proton NMR methods and molecular modeling. The primary sequence of the protein does not share similarities with other known toxins. It includes six cysteines forming three disulfide bridges. However, because of PA1b resistance to protease cleavage, conventional methods failed to establish the connectivity pattern. Our first attempts to assign the disulfide network from NOE data alone remained unsuccessful due to the tight packing of the cysteine residues within the core of the molecule. Yet, the use of ambiguous disulfide restraints within ARIA allowed us to establish that PA1b belongs to the inhibitor cystine-knot family. It exhibits the structural features that are characteristic of the knottin fold, namely, a triple-stranded antiparallel beta-sheet with a long flexible loop connecting the first to the second strand and a series of turns. A comparison of the structural properties of PA1b with that of structurally related proteins adopting a knottin fold and exhibiting a diverse range of biological activities shows that the electrostatic and lipophilic potentials at the surface of PA1b are very close to those found for the spider toxin ACTX-Hi:OB4219, thereby suggesting activity on ion channels.

PubMed: 14556622
DOI: 10.1021/bi034803l

Experimental method

SOLUTION NMR