Spectroscopic and photothermal study of myoglobin conformational changes in the presence of sodium dodecyl sulfate Article

Mikšovská, J, Yom, J, Diamond, B et al. (2006). Spectroscopic and photothermal study of myoglobin conformational changes in the presence of sodium dodecyl sulfate . 7(2), 476-482. 10.1021/bm0506703

cited authors

  • Mikšovská, J; Yom, J; Diamond, B; Larsen, RW

authors

abstract

  • Interactions between sodium dodecyl sulfate (SDS) and horse heart myoglobin (Mb) at surfactant concentrations below the critical micelle concentration have been studied using steady-state and transient absorption spectroscopies and photoacoustic calorimetry. SDS binding to Mb induces a heme transition from high-spin five-coordinate to low-spin six-coordinate in met- and deoxyMb, with the distal His residue likely to be the sixth ligand. The transition is complete at an SDS concentration of ∼350 μM and ∼700 μM for met- and deoxyMb, respectively. ΔGH2O and m values determined from equilibrium SDS-induced unfolding curves indicate similar stability of met- and deoxyMb toward unfolding; however, the larger m value for the deoxyMb equilibrium intermediate indicates that its structure differs from that of metMb. Results from transient absorption spectroscopy show that CO rebinding to Fe2+-Mb in the presence of SDS is a biphasic process with the rate constant of the first process approximately 5.5 × 103 s-1, whereas the second process displays a rate similar to that for CO rebinding to native Mb (kobs = 7.14 × 102 s-1) at 1 mM CO. Results of photoacoustic calorimetry show that CO dissociation from deoxyMb occurs more than 10 times faster in the presence of SDS than in native Mb. These data suggest that the heme binding pocket is more solvent-exposed in the SDS-induced equilibrium intermediate relative to native Mb, which is likely due to the electrostatic and hydrophobic interactions between surfactant molecules and the protein matrix. © 2006 American Chemical Society.

publication date

  • February 1, 2006

Digital Object Identifier (DOI)

start page

  • 476

end page

  • 482

volume

  • 7

issue

  • 2