Bis （1-diethylphosphino-2-diphenylphosphino ethane）-bis （dinitrogen） molybdenum （O）, Mo（N2）2 （Ph2POH2CH2PEt2）2, is a new dinitrogen complex synthesized by Chen Jiabi et al.
Molecular modeling of interactions of four 7- or 8-substituted benzolactam-V8 （BLV） molecules with the cys2 activator-binding domain of protein kinase C （PKCδ） was carried out using molecular docking program Auto...Molecular modeling of interactions of four 7- or 8-substituted benzolactam-V8 （BLV） molecules with the cys2 activator-binding domain of protein kinase C （PKCδ） was carried out using molecular docking program Autodock. The docked models reveal that the hydroxymethyl group at the C（5） atom of the eight-membered ring of each BLV is bound at the bottom of the binding groove of the cys2 domain of PKCδ The BLV molecules make hydrogen bonds and hydrophobic interactions with PKCδ, which are similar to those in the crystal structure of the cys2 domain of PKCδ in complex with phorbol 13-acetate. BLV-1 does not contain a long side chain that is hydrophobic and necessary for membrane insertion, so that it would not be a potent modulator of PKCδ. The other three BLV molecules have long side chains substituted at C（7） or C（8） atoms, and it was predicted, based on the docking results, that they had the PKCδ-binding affinity in the order of BLV-2〉BLV-4〉BLV-3, and BLV-2 would be a potent activator of PKCδ.展开更多
The mutation sites of the four mutants F35Y, P40V, V45E and V45Y of cytochrome b 5 are located at the edge of the heme binding pocket. The solvent accessible areas of the “pocket interior” of the four mutants ...The mutation sites of the four mutants F35Y, P40V, V45E and V45Y of cytochrome b 5 are located at the edge of the heme binding pocket. The solvent accessible areas of the “pocket interior” of the four mutants and the wild type cytochrome b 5 have been calculated based on their crystal structures at high resolution. The change in the hydrophobicity of the heme binding pocket resulting from the mutation can be quantitatively described using the difference of the solvent accessible area of the “pocket interior” of each mutant from that of the wild type cytochrome b 5. The influences of the hydrophobicity of the heme binding pocket on the protein stability and redox potential are discussed.展开更多
Glu44, Glu48, Glu56 and Asp60 are the negatively charged residues located at the molecular surface of cytochrome b 5. Two mutants of cytochrome b 5 were prepared, in which two or all of these four residues were muta...Glu44, Glu48, Glu56 and Asp60 are the negatively charged residues located at the molecular surface of cytochrome b 5. Two mutants of cytochrome b 5 were prepared, in which two or all of these four residues were mutated to alanines. The mutations give rise to slightly positive shifts of the redox potentials of cytochrome b 5 and obvious decrease of the cytochrome b 5-cytochrome c binding constants and electron transfer rates. The crystal structures of the two mutants were determined at 0.18 nm resolution, showing no alteration in overall structures and exhibiting slight changes in the local conformations around the mutation sites as compared with the wild-type protein. Based on the crystal structure of the quadruple-site mutant, a model for the binding of this mutant with cytochrome c is proposed, which involves the salt bridges from Glu37, Glu38 and heme propionate of cytochrome b 5 to three lysines of cytochrome c and can well account for the properties and behaviors of this mutant.展开更多
In order to illustrate the roles played by Pro40 in the structure, properties and functions of Cytochrome b 5, three mutated genes, P40V, P40Y, P40G were constructed in this work. Only the P40V gene was successfully ...In order to illustrate the roles played by Pro40 in the structure, properties and functions of Cytochrome b 5, three mutated genes, P40V, P40Y, P40G were constructed in this work. Only the P40V gene was successfully expressed into holoprotein in E. coli JM83. According to the results of X-ray crystallographic analysis and various kinds of spectroscopy studies, it is evident that substituting valine for Pro40 does not result in significant alterations in the protein's overall structure; however, local conformational perturbations in the proximity of the heme do occur. The redox potential of the P40V mutant is 40 mV lower than that of the wild type protein. Its stability towards heat, urea, acid and ethanol were significantly decreased. The mutation leads to a decrease in the hydrophobicity of the heme pocket, which is probably the major factor contributing to the above changes. Binding constants and electron transfer rates between cytochrome b 5 and cytochrome c were determined using UV-visible spectroscopy and stopped-flow techniques for both the wild type and the mutant. The results showed that the substitution of Pro40 by valine does not influence the binding constant of cytochrome b 5 to cytochrome c; however, the electron transfer rate between them decreased significantly. This indicates that proline-40 is essential to maintaining cytochrome b 5's stability and its electron transfer with cytochrome c. These studies also provided a good example that property and functional changes of a protein do not necessarily require large overall structural alterations; in most cases, only perturbations on the local conformations are sufficient to induce significant changes in protein′s properties and functions.展开更多
文摘Bis （1-diethylphosphino-2-diphenylphosphino ethane）-bis （dinitrogen） molybdenum （O）, Mo（N2）2 （Ph2POH2CH2PEt2）2, is a new dinitrogen complex synthesized by Chen Jiabi et al.
基金Project supported by the National Natural Science Foundation of China （No. 30370335）.
文摘Molecular modeling of interactions of four 7- or 8-substituted benzolactam-V8 （BLV） molecules with the cys2 activator-binding domain of protein kinase C （PKCδ） was carried out using molecular docking program Autodock. The docked models reveal that the hydroxymethyl group at the C（5） atom of the eight-membered ring of each BLV is bound at the bottom of the binding groove of the cys2 domain of PKCδ The BLV molecules make hydrogen bonds and hydrophobic interactions with PKCδ, which are similar to those in the crystal structure of the cys2 domain of PKCδ in complex with phorbol 13-acetate. BLV-1 does not contain a long side chain that is hydrophobic and necessary for membrane insertion, so that it would not be a potent modulator of PKCδ. The other three BLV molecules have long side chains substituted at C（7） or C（8） atoms, and it was predicted, based on the docking results, that they had the PKCδ-binding affinity in the order of BLV-2〉BLV-4〉BLV-3, and BLV-2 would be a potent activator of PKCδ.
文摘The mutation sites of the four mutants F35Y, P40V, V45E and V45Y of cytochrome b 5 are located at the edge of the heme binding pocket. The solvent accessible areas of the “pocket interior” of the four mutants and the wild type cytochrome b 5 have been calculated based on their crystal structures at high resolution. The change in the hydrophobicity of the heme binding pocket resulting from the mutation can be quantitatively described using the difference of the solvent accessible area of the “pocket interior” of each mutant from that of the wild type cytochrome b 5. The influences of the hydrophobicity of the heme binding pocket on the protein stability and redox potential are discussed.
文摘Glu44, Glu48, Glu56 and Asp60 are the negatively charged residues located at the molecular surface of cytochrome b 5. Two mutants of cytochrome b 5 were prepared, in which two or all of these four residues were mutated to alanines. The mutations give rise to slightly positive shifts of the redox potentials of cytochrome b 5 and obvious decrease of the cytochrome b 5-cytochrome c binding constants and electron transfer rates. The crystal structures of the two mutants were determined at 0.18 nm resolution, showing no alteration in overall structures and exhibiting slight changes in the local conformations around the mutation sites as compared with the wild-type protein. Based on the crystal structure of the quadruple-site mutant, a model for the binding of this mutant with cytochrome c is proposed, which involves the salt bridges from Glu37, Glu38 and heme propionate of cytochrome b 5 to three lysines of cytochrome c and can well account for the properties and behaviors of this mutant.
文摘In order to illustrate the roles played by Pro40 in the structure, properties and functions of Cytochrome b 5, three mutated genes, P40V, P40Y, P40G were constructed in this work. Only the P40V gene was successfully expressed into holoprotein in E. coli JM83. According to the results of X-ray crystallographic analysis and various kinds of spectroscopy studies, it is evident that substituting valine for Pro40 does not result in significant alterations in the protein's overall structure; however, local conformational perturbations in the proximity of the heme do occur. The redox potential of the P40V mutant is 40 mV lower than that of the wild type protein. Its stability towards heat, urea, acid and ethanol were significantly decreased. The mutation leads to a decrease in the hydrophobicity of the heme pocket, which is probably the major factor contributing to the above changes. Binding constants and electron transfer rates between cytochrome b 5 and cytochrome c were determined using UV-visible spectroscopy and stopped-flow techniques for both the wild type and the mutant. The results showed that the substitution of Pro40 by valine does not influence the binding constant of cytochrome b 5 to cytochrome c; however, the electron transfer rate between them decreased significantly. This indicates that proline-40 is essential to maintaining cytochrome b 5's stability and its electron transfer with cytochrome c. These studies also provided a good example that property and functional changes of a protein do not necessarily require large overall structural alterations; in most cases, only perturbations on the local conformations are sufficient to induce significant changes in protein′s properties and functions.
