Mechanism of formation of the C-terminal beta-hairpin of the B3 domain of the immunoglobulin binding protein G from Streptococcus. III. Dynamics of long-range hydrophobic interactions.
A 20-residue peptide, IG(42-61), derived from the C-terminal beta-hairpin of the B3 domain of the immunoglobulin binding protein G from Streptoccocus was studied using circular dichroism, nuclear magnetic resonance (NMR) spectroscopy at various temperatures and by differential scanning calorimetry (DSC). Unlike other related peptides studied so far, this peptide displays two heat capacity peaks in DSC measurements (at a scanning rate of 1.5 deg/min at a peptide concentration of 0.07 mM), which suggests a three-state folding/unfolding process. The results from DSC and NMR measurements suggest the formation of a dynamic network of hydrophobic interactions stabilizing the structure, which resembles a beta-hairpin shape over a wide range of temperatures (283-313 K). Our results show that IG (42-61) possesses a well-organized three-dimensional structure stabilized by long-range hydrophobic interactions (Tyr50 ... Phe57 and Trp48 ... Val59) at T = 283 K and (Trp48 ... Val59) at 305 and 313 K. The mechanism of beta-hairpin folding and unfolding, as well as the influence of peptide length on its conformational properties, are also discussed.
Laboratory of Biopolymer Structure, Intercollegiate Faculty of Biotechnology, University of Gdańsk, Medical University of Gdańsk, Kładki 24, 80-822 Gdańsk, Poland.
Agnieszka
A
Lewandowska
Stanisław
S
Ołdziej
Adam
A
Liwo
Harold A
HA
Scheraga
D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D057927:Hydrophobic and Hydrophilic Interactions; D008956:Models, Chemical; D056004:Molecular Dynamics Simulation; D019906:Nuclear Magnetic Resonance, Biomolecular; D055550:Protein Stability; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013696:Temperature; D013816:Thermodynamics
D001426:Bacterial Proteins; C034284:IgG Fc-binding protein, Streptococcus