TY - JOUR
T1 - Dimer-to-tetramer transformation
T2 - Loop excision dramatically alters structure and stability of the ROP four α-helix bundle protein
AU - Lassalle, Michael W.
AU - Hinz, Hans Jürgen
AU - Wenzel, Herbert
AU - Vlassi, Metaxia
AU - Kokkinidis, Michael
AU - Cesareni, Giovanni
PY - 1998/6/19
Y1 - 1998/6/19
N2 - The ROP loop excision mutant RM6 shows dramatic changes in structure and stability in comparison to the wild-type protein. Removal of the five amino acids (Asp30, Ala31, Asp32, Glu33, Gln34) from the loop results in a complete reorganization of the protein as evidenced by single crystal X-ray analysis and thermodynamic unfolding studies. The homodimeric four-α-helix motif of the wild-type structure is given up. Instead a homotetrameric four-α-helix structure with extended, loop-free helical monomers is formed. This intriguing structural change is associated with the acquisition of hyperthermophilic stability. This is evident in the shift in transition temperature from 71°C characteristic of the wild-type protein to 101°C for RM6. Accordingly the Gibbs energy of unfolding is increased from 71.7 kJ (mol of dimer)-1 to 195.1 kJ (mol of tetramer)-1 The tetramer-to-monomer transition proceeds highly cooperatively involving an enthalpy change of ΔH = 1073 ± 30 kJ (mol of tetramer)-1 and a heat capacity change at the transition temperature of Δ(N)(D)C(p) = 14.9 (±) 3% kJ (mol of tetramer x K)-1. The two-state nature of the unfolding reaction is reflected in coinciding calorimetric and van't Hoff enthalpy values.
AB - The ROP loop excision mutant RM6 shows dramatic changes in structure and stability in comparison to the wild-type protein. Removal of the five amino acids (Asp30, Ala31, Asp32, Glu33, Gln34) from the loop results in a complete reorganization of the protein as evidenced by single crystal X-ray analysis and thermodynamic unfolding studies. The homodimeric four-α-helix motif of the wild-type structure is given up. Instead a homotetrameric four-α-helix structure with extended, loop-free helical monomers is formed. This intriguing structural change is associated with the acquisition of hyperthermophilic stability. This is evident in the shift in transition temperature from 71°C characteristic of the wild-type protein to 101°C for RM6. Accordingly the Gibbs energy of unfolding is increased from 71.7 kJ (mol of dimer)-1 to 195.1 kJ (mol of tetramer)-1 The tetramer-to-monomer transition proceeds highly cooperatively involving an enthalpy change of ΔH = 1073 ± 30 kJ (mol of tetramer)-1 and a heat capacity change at the transition temperature of Δ(N)(D)C(p) = 14.9 (±) 3% kJ (mol of tetramer x K)-1. The two-state nature of the unfolding reaction is reflected in coinciding calorimetric and van't Hoff enthalpy values.
KW - Cooperativity
KW - Hyperthermophilic stability
KW - Loop excision
KW - ROP
KW - Tetramer formation
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U2 - 10.1006/jmbi.1998.1776
DO - 10.1006/jmbi.1998.1776
M3 - Article
C2 - 9642076
AN - SCOPUS:0032546744
VL - 279
SP - 987
EP - 1000
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
SN - 0022-2836
IS - 4
ER -