2ipj: Difference between revisions
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New page: left|200px<br /> <applet load="2ipj" size="450" color="white" frame="true" align="right" spinBox="true" caption="2ipj, resolution 1.800Å" /> '''Crystal structure ... |
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[[Image:2ipj.gif|left|200px]]<br /> | [[Image:2ipj.gif|left|200px]]<br /><applet load="2ipj" size="350" color="white" frame="true" align="right" spinBox="true" | ||
<applet load="2ipj" size=" | |||
caption="2ipj, resolution 1.800Å" /> | caption="2ipj, resolution 1.800Å" /> | ||
'''Crystal structure of h3alpha-hydroxysteroid dehydrogenase type 3 mutant Y24A in complex with NADP+ and epi-testosterone'''<br /> | '''Crystal structure of h3alpha-hydroxysteroid dehydrogenase type 3 mutant Y24A in complex with NADP+ and epi-testosterone'''<br /> | ||
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==Overview== | ==Overview== | ||
The mouse 17alpha-hydroxysteroid dehydrogenase (m17alpha-HSD) is the, unique known member of the aldo-keto reductase (AKR) superfamily able to, catalyze efficiently and in a stereospecific manner the conversion of, androstenedione (Delta4) into epi-testosterone (epi-T), the 17alpha-epimer, of testosterone. Structural and mutagenic studies had already identified, one of the residues delineating the steroid-binding cavity, A24, as the, major molecular determinant for the stereospecificity of m17alpha-HSD. We, report here a ternary complex crystal structure, (m17alpha-HSD:NADP(+):epi-T) determined at 1.85 A resolution that confirms, this and reveals a unique steroid-binding mode for an AKR enzyme. Indeed, in addition to the interactions found in all other AKRs (van der Waals, contacts stabilizing the core of the steroid and the hydrogen bonds, established at the catalytic site by the Y55 and H117 residues with the, oxygen atom of the ketone group to be reduced), m17alpha-HSD establishes, with the other extremity of the steroid nucleus an additional interaction, involving K31. By combining direct mutagenesis and kinetic studies, we, found that the elimination of this hydrogen bond did not affect the, affinity of the enzyme for its steroid substrate but led to a slight but, significant increase of its catalytic efficiency (k(cat)/K(m)), suggesting, a role for K31 in the release of the steroidal product at the end of the, reaction. This previously unobserved steroid-binding mode for an AKR is, similar to that adopted by other steroid-binding proteins, the, hydroxysteroid dehydrogenases of the short-chain dehydrogenases/reductases, (SDR) family and the steroid hormone nuclear receptors. Mutagenesis and, structural studies made on the human type 3 3alpha-HSD, a closely related, enzyme that shares 73% amino acids identity with the m17alpha-HSD, also, revealed that the residue at position 24 of these two enzymes directly, affects the binding and/or the release of NADPH, in addition to its role, in their 17alpha/17beta stereospecificity. | The mouse 17alpha-hydroxysteroid dehydrogenase (m17alpha-HSD) is the, unique known member of the aldo-keto reductase (AKR) superfamily able to, catalyze efficiently and in a stereospecific manner the conversion of, androstenedione (Delta4) into epi-testosterone (epi-T), the 17alpha-epimer, of testosterone. Structural and mutagenic studies had already identified, one of the residues delineating the steroid-binding cavity, A24, as the, major molecular determinant for the stereospecificity of m17alpha-HSD. We, report here a ternary complex crystal structure, (m17alpha-HSD:NADP(+):epi-T) determined at 1.85 A resolution that confirms, this and reveals a unique steroid-binding mode for an AKR enzyme. Indeed, in addition to the interactions found in all other AKRs (van der Waals, contacts stabilizing the core of the steroid and the hydrogen bonds, established at the catalytic site by the Y55 and H117 residues with the, oxygen atom of the ketone group to be reduced), m17alpha-HSD establishes, with the other extremity of the steroid nucleus an additional interaction, involving K31. By combining direct mutagenesis and kinetic studies, we, found that the elimination of this hydrogen bond did not affect the, affinity of the enzyme for its steroid substrate but led to a slight but, significant increase of its catalytic efficiency (k(cat)/K(m)), suggesting, a role for K31 in the release of the steroidal product at the end of the, reaction. This previously unobserved steroid-binding mode for an AKR is, similar to that adopted by other steroid-binding proteins, the, hydroxysteroid dehydrogenases of the short-chain dehydrogenases/reductases, (SDR) family and the steroid hormone nuclear receptors. Mutagenesis and, structural studies made on the human type 3 3alpha-HSD, a closely related, enzyme that shares 73% amino acids identity with the m17alpha-HSD, also, revealed that the residue at position 24 of these two enzymes directly, affects the binding and/or the release of NADPH, in addition to its role, in their 17alpha/17beta stereospecificity. | ||
==About this Structure== | ==About this Structure== | ||
2IPJ is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with SO4, NAP, FFA, BME and EDO as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http:// | 2IPJ is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with <scene name='pdbligand=SO4:'>SO4</scene>, <scene name='pdbligand=NAP:'>NAP</scene>, <scene name='pdbligand=FFA:'>FFA</scene>, <scene name='pdbligand=BME:'>BME</scene> and <scene name='pdbligand=EDO:'>EDO</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2IPJ OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: open conformation]] | [[Category: open conformation]] | ||
''Page seeded by [http:// | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Wed Jan 23 14:49:17 2008'' | ||
