3plc
Crystal structure of Beta-Cardiotoxin, a novel three-finger cardiotoxin from the venom of Ophiophagus hannah
Structural highlights
Function3SDC7_OPHHA Acts as a beta-blocker by binding to beta-1 and beta-2 adrenergic receptors (ADRB1 and ADRB2). It dose-dependently decreases the heart rate (bradycardia), whereas conventional cardiotoxins increases it. At 100 mg/kg, intraperitoneal injection into mice provokes labored breathing, impaired locomotion, lack of response to external stimuli, and death (after 30 min).[1] Publication Abstract from PubMedbeta-Cardiotoxin is a novel member of the snake venom three-finger toxin (3FTX) family. This is the first exogenous protein to antagonize beta-adrenergic receptors and thereby causing reduction in heart rates (bradycardia) when administered into animals, unlike the conventional cardiotoxins as reported earlier. 3FTXs are stable all beta-sheet peptides with 60-80 amino acid residues. Here, we describe the three-dimensional crystal structure of beta-cardiotoxin together with the identification of a molten globule intermediate in the unfolding pathway of this protein. In spite of the overall structural similarity of this protein with conventional cardiotoxins, there are notable differences observed at the loop region and in the charge distribution on the surface, which are known to be critical for cytolytic activity of cardiotoxins. The molten globule intermediate state present in the thermal unfolding pathway of beta-cardiotoxin was however not observed during the chemical denaturation of the protein. Interestingly, circular dichroism (CD) and NMR studies revealed the presence of alpha-helical secondary structure in the molten globule intermediate. These results point to substantial conformational plasticity of beta-cardiotoxin, which might aid the protein in responding to the sometimes conflicting demands of structure, stability, and function during its biological lifetime. Identification of a alpha-helical molten globule intermediate and structural characterization of beta-cardiotoxin, an all beta-sheet protein isolated from the venom of Ophiophagus hannah (king cobra).,Roy A, Qingxiang S, Alex C, Rajagopalan N, Jobichen C, Sivaraman J, Kini RM Protein Sci. 2019 May;28(5):952-963. doi: 10.1002/pro.3605. Epub 2019 Apr 4. PMID:30891862[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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