TY - JOUR
T1 - Structural mechanism governing cis and trans isomeric states and an intramolecular switch for cis/trans isomerization of a non-proline peptide bond observed in crystal structures of scorpion toxins
AU - Guan, Rong Jin
AU - Xiang, Ye
AU - He, Xiao Lin
AU - Wang, Chun Guang
AU - Wang, Miao
AU - Zhang, Ying
AU - Sundberg, Eric J.
AU - Wang, Da Cheng
N1 - Funding Information:
This work was supported by Grants from the NNSF (30370320), the MOST (G19990756, 2002BA711A13) and the CAS (KSCX1-SW-17). Data collection was supported by KEK (00G290). We thank Professor N. Sakabe for his help during data collection in Photon Factory in Japan.
PY - 2004/8/27
Y1 - 2004/8/27
N2 - Non-proline cis peptide bonds have been observed in numerous protein crystal structures even though the energetic barrier to this conformation is significant and no non-prolyl-cis/trans-isomerase has been identified to date. While some external factors, such as metal binding or co-factor interaction, have been identified that appear to induce cis/trans isomerization of non-proline peptide bonds, the intrinsic structural basis for their existence and the mechanism governing cis/trans isomerization in proteins remains poorly understood. Here, we report the crystal structure of a newly isolated neurotoxin, the scorpion α-like toxin Buthus martensii Karsch (BmK) M7, at 1.4 Å resolution. BmK M7 crystallizes as a dimer in which the identical non-proline peptide bond between residues 9 and 10 exists either in the cis conformation or as a mixture of cis and trans conformations in either monomer. We also determined the crystal structures of several mutants of BmK M1, a representative scorpion α-like toxin that contains an identical non-proline cis peptide bond as that observed in BmK M7, in which residues within or neighboring the cis peptide bond were altered. Substitution of an aspartic acid residue for lysine at residue 8 in the BmK M1 (K8D) mutant converted the cis form of the non-proline peptide bond 9-10 into the trans form, revealing an intramolecular switch for cis-to-trans isomerization. Cis/trans interconversion of the switch residue at position 8 appears to be sequence-dependent as the peptide bond between residues 9 and 10 retains its wild-type cis conformation in the BmK M1 (K8Q) mutant structure. The structural interconversion of the isomeric states of the BmK M1 non-proline cis peptide bond may relate to the conversion of the scorpion α-toxins subgroups.
AB - Non-proline cis peptide bonds have been observed in numerous protein crystal structures even though the energetic barrier to this conformation is significant and no non-prolyl-cis/trans-isomerase has been identified to date. While some external factors, such as metal binding or co-factor interaction, have been identified that appear to induce cis/trans isomerization of non-proline peptide bonds, the intrinsic structural basis for their existence and the mechanism governing cis/trans isomerization in proteins remains poorly understood. Here, we report the crystal structure of a newly isolated neurotoxin, the scorpion α-like toxin Buthus martensii Karsch (BmK) M7, at 1.4 Å resolution. BmK M7 crystallizes as a dimer in which the identical non-proline peptide bond between residues 9 and 10 exists either in the cis conformation or as a mixture of cis and trans conformations in either monomer. We also determined the crystal structures of several mutants of BmK M1, a representative scorpion α-like toxin that contains an identical non-proline cis peptide bond as that observed in BmK M7, in which residues within or neighboring the cis peptide bond were altered. Substitution of an aspartic acid residue for lysine at residue 8 in the BmK M1 (K8D) mutant converted the cis form of the non-proline peptide bond 9-10 into the trans form, revealing an intramolecular switch for cis-to-trans isomerization. Cis/trans interconversion of the switch residue at position 8 appears to be sequence-dependent as the peptide bond between residues 9 and 10 retains its wild-type cis conformation in the BmK M1 (K8Q) mutant structure. The structural interconversion of the isomeric states of the BmK M1 non-proline cis peptide bond may relate to the conversion of the scorpion α-toxins subgroups.
KW - cis/trans isomerization
KW - crystal structure
KW - intramolecular switch
KW - non-proline peptide bond
KW - structural mechanism
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U2 - 10.1016/j.jmb.2004.06.067
DO - 10.1016/j.jmb.2004.06.067
M3 - Article
C2 - 15321715
AN - SCOPUS:4143091852
SN - 0022-2836
VL - 341
SP - 1189
EP - 1204
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
IS - 5
ER -