Folding Kinetics of a Naturally Occurring Helical Peptide: Implication of the Folding Speed Limit of Helical Proteins

• DOI: 10.1021/jp801721p
• Publication Date: 2008-07-09T10:01:50Z
• Authors: Smita Mukherjee; Pramit Chowdhury; Michelle R. Bunagan; Feng Gai
• Keywords: Folding (DSP implementation); Temperature jump; Contact order; Helix (gastropod); Alanine

The folding mechanism and dynamics of a helical protein may strongly depend on how quickly its constituent α-helices can fold independently. Thus, our understanding the problem be greatly enhanced by systematic survey rates individual α-helical segments derived from their parent proteins. As first step, we have studied relaxation kinetics central helix (L9:41-74) ribosomal L9 bacterium Bacillus stearothermophilus, in response to temperature-jump (T-jump) using infrared spectroscopy. L9:41-74 has been shown exhibit unusually high helicity aqueous solution due series side chain-side chain interactions, most which are electrostatic nature, while still remaining monomeric over wide concentration range. this peptide represents an excellent model system not only for examining rate naturally occurring helices differs that widely alanine-based peptides, but also estimating speed limit (small) Our results show T-jump induced is significantly slower than peptides. For example, at 11 °C time constant about 2 μs, roughly seven times SPE5, alanine-rich similar length. In addition, truncated version even slower. Taken together, these suggest proteins scale Furthermore, argue measured between 8 45 provides realistic estimate ultimate temperature