Download MendeleyThe omega-loop of cobra cytotoxins tolerates multiple amino acid substitutions.
Dubinnyi, M.A., Dubovskii, P.V., Starkov, V.G., Utkin, Y.N.(2021) Biochem Biophys Res Commun 558: 141-146
- PubMed: 33915327
- DOI: https://doi.org/10.1016/j.bbrc.2021.04.069
- Primary Citation of Related Structures:
6RC7, 7O2K - PubMed 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 13 C, 15 N 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.
Organizational Affiliation:
Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya str., Moscow, 117997, Russia; Moscow Institute of Physics and Technology (State University), 9 Institutskiy per., Dolgoprudny, Moscow Region, 141700, Russia.
