Thermodynamic and mechanistic insights into coupled binding and unwinding of collagen by matrix metalloproteinase 1

Local unwinding of the collagen triple helix is a necessary step for initiating the collagen degradation cascade in extracellular matrices. A few matrix metalloproteinases (MMPs) are known to support this key process, but its energetic aspects remain unknown. Here, we captured the thermodynamics of the triple helix unwinding by monitoring interactions between a collagen peptide and MMP-1(E200A) - an active-site mutant of an archetypal vertebrate collagenase - at increasing temperatures, using isothermal titration calorimetry (ITC). Coupled binding and unwinding manifests as a curved relationship between the total enthalpy change and temperature of the reaction, producing increasingly negative heat capacity change ({Delta}{Delta}Cp {approx} -36.3 kcal/molK2). A specially designed solid-phase binding and cleavage assay (SPBCA) reported strain in the catalytically relevant unwound state, suggesting that this state is distinct from the horizon of sampled conformations of the collagenase-susceptible site. MMP-1 appears to blend selected fit with induced fit mechanisms to catalyse collagen unwinding prior to cleavage of individual collagen chains. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=164 SRC="FIGDIR/small/272104v1_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@33fb68org.highwire.dtl.DTLVardef@be9408org.highwire.dtl.DTLVardef@1e8aa03org.highwire.dtl.DTLVardef@1f1cbbc_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIThe unwinding of the collagen triple helix by matrix metalloproteinases (MMPs) is critical for collagen catabolism, but how MMPs harness bioavailable energy for this energetically expensive process is enigmatic C_LIO_LIRising temperature causes linear increases of the negative heat capacity change associated with the interaction of MMP-1 with a collagenase-susceptible triple-helical peptide, indicating enrichment of hydrophobic contacts during the triple helix unwinding C_LIO_LIThe complex of MMP-1 with locally unwound collagen holds considerable structural strain, which becomes relieved upon cleavage of the unwound collagen strand(s) C_LIO_LIMMP-1 consumes heat to drive specific (structurally distinct) collagen unwinding by increasing entropy associated with evolving hydrophobic anchor points between the enzyme and the substrate C_LIO_LIThe prototypic collagenase MMP-1 appears to blend conformational selection with induced fit, shedding light on the thermodynamic principles by which MMPs trigger collagen breakdown and supporting general mechanistic conclusions concerning conformational changes coupled to protein-protein binding C_LI