1nb1
From Proteopedia
High resolution solution structure of kalata B1
Structural highlights
Function[KAB1_OLDAF] Probably participates in a plant defense mechanism. Has antibiotic activity. Has a diuretic effect. Has a uterotonic effect in humans. Active against the Gram-positive S.aureus with a minimum inhibition concentration of approximately 0.2 microM. Relatively ineffective against Gram-negative bacteria such as E.coli and P.aeruginosa. Inhibitory effect on the growth and development of larvae from H.punctigera. The unmodified form has hemolytic activity, the oxidized form lacks hemolytic activity. If the protein is linearized, hemolytic activity is lost.[1] [2] Publication Abstract from PubMedIn recent years an increasing number of miniproteins containing an amide-cyclized backbone have been discovered. The cyclotide family is the largest group of such proteins and is characterized by a circular protein backbone and six conserved cysteine residues linked by disulfide bonds in a tight core of the molecule. These form a cystine knot in which an embedded ring formed by two of the disulfide bonds and the connecting backbone segment is threaded by a third disulfide bond. In the current study we have undertaken high resolution structural analysis of two prototypic cyclotides, kalata B1 and cycloviolacin O1, to define the role of the conserved residues in the sequence. We provide the first comprehensive analysis of the topological features in this unique family of proteins, namely rings (a circular backbone), twists (a cis-peptide bond in the Mobius cyclotides) and knots (a knotted arrangement of the disulfide bonds). Twists, knots, and rings in proteins. Structural definition of the cyclotide framework.,Rosengren KJ, Daly NL, Plan MR, Waine C, Craik DJ J Biol Chem. 2003 Mar 7;278(10):8606-16. Epub 2002 Dec 12. PMID:12482868[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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