Solution structure of a FK binding protein: Schistosoma mansoni protein (Smp50) from trematode

Author(s): Jonathan Penoyar, Herbert Iijima, Arindam Sen, Ahmed Osman

Recently a 50 kilodalton FKBP protein (Smp50) fromthe trematode Schistosoma mansoni was produced in bacteria and shown to have biological activity. We present here in this paper a detailed investigation of the secondary structure of this protein fromCircular Dichroism(CD) and Fourier Transform Infra-red (FTIR) spectroscopic techniques. We investigated the effect of temperature, pH and salt and solvent compositions on the secondary structure of Smp50. At room temperature and in a phosphate buffer (pH 7.1) Smp50 has 26%-helix, 42%-structure and 31%random coil structure and at 0C, the amount of -helix increases to 32% with a 36% -structure and a 33% random coil. When the pH is lowered to 4.0 with an acetate buffer, the -helix decreases to 29%. Our results indicate that the protein is not destroyed at high temperatures, retaining as much as 20 % -helix even at 80C. From an analysis of the FTIR spectrum, Smp50 has 28%-helix, 42%-structure and a 30%randomcoil structure, which is in excellent agreement with the CD results. Our results indicate that the protein has an highly extended -structure in solution and gives a high degree of stability to the protein based on our temperature and pH variation studies.

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