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Conformational fluctuations in anthrax protective antigen: a possible role of calcium in the folding pathway of the protein
Author(s) -
Gupta Pradeep K,
Chandra Harish,
Gaur Reetika,
Kurupati Raj K,
Chowdhury Shantanu,
Tandon Vibha,
Singh Yogendra,
Maithal Kapil
Publication year - 2003
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(03)01226-2
Subject(s) - anthrax toxin , proteolysis , chemistry , calcium , denaturation (fissile materials) , protein folding , biophysics , cytosol , folding (dsp implementation) , protein structure , biochemistry , antigen , biology , enzyme , recombinant dna , fusion protein , genetics , organic chemistry , engineering , nuclear chemistry , electrical engineering , gene
Protective antigen (PA) is the central receptor binding component of anthrax toxin, which translocates catalytic components of the toxin into the cytosol of mammalian cells. Ever since the crystal structure of PA was solved, there have been speculations regarding the possible role of calcium ions present in domain I of the protein. We have carried out a systematic study to elucidate the effect of calcium removal on the structural stability of PA using various optical spectroscopic techniques, limited proteolysis and mutational analysis. Urea denaturation studies clearly suggest that the unfolding pathway of the protein follows a non‐two state transition with apo‐PA being an intermediate species, whereas the folding pathway shows that calcium ions may be critical for the initial protein assembly.