PDBsum entry 7o2k

Toxin

PDB id: 7o2k

Contents

Protein chain

60 a.a.

Waters ×3

PDB id:

7o2k

Name:

Toxin

Title:

Nmr solution structue of cytotoxin 2 from naja kaouthia

Structure:

Cytotoxin 2. Chain: a. Synonym: cx2,toxin cm-7a

Source:

Naja kaouthia. Monocled cobra, naja siamensis. Organism_taxid: 8649

NMR struc:

20 models

Authors:

M.A.Dubinnyi,P.V.Dubovskii

Key ref:

M.A.Dubinnyi et al. (2021). The omega-loop of cobra cytotoxins tolerates multiple amino acid substitutions. Biochem Biophys Res Commun, 558, 141-146. PubMed id: 33915327 DOI: 10.1016/j.bbrc.2021.04.069

Date:

30-Mar-21 Release date: 02-Jun-21

Protein chain

P01445  (3SA7A_NAJKA) -  Cytotoxin 2 from Naja kaouthia

Seq: 60 a.a.

Struc: 60 a.a.

DOI no: 10.1016/j.bbrc.2021.04.069

Biochem Biophys Res Commun 558:141-146 (2021)

PubMed id: 33915327

The omega-loop of cobra cytotoxins tolerates multiple amino acid substitutions.

M.A.Dubinnyi, P.V.Dubovskii, V.G.Starkov, Y.N.Utkin.

ABSTRACT

Cobra cytotoxins (CTs), the three-fingered proteins, feature high amino acid sequence homology in the beta-strands and variations in the loop regions. We selected a pair of cytotoxins from Naja kaouthia crude venom to clarify the sequence-structure relationships. Using chromatography and mass spectroscopy, we separated and identified the mixture of cytotoxins 2 and 3, differentiated by the only Val 41/Ala 41 substitution. Here, using natural abundance ¹³C, ¹⁵N NMR-spectroscopy we performed chemical shift assignments of the signals of the both toxins in aqueous solution in the major and minor forms. Combining NOE and chemical shift data, the toxins' spatial structure was determined. Finally, we proved that the tip of the "finger"-2, or the loop-2 of cytotoxins adopts the shape of an omega-loop with a tightly-bound water molecule in its cavity. Comparison with other NMR and X-ray structures of cytotoxins possessing different amino acid sequences reveals spatial similarity in this family of proteins, including the loop-2 region, previously considered to be flexible.