Sandbox Reserved 774: Difference between revisions
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=Structure= | =Structure= | ||
Has a chain structure with 2.4 A resolution, and 2.9 A resolution with a co-factor (acetyl-CoA).<ref name=Shiva/> The method used to determine the structure was [[X-ray crystallography]]. Sedimentation and crystal structure analysis clearly shows that Hpa2 is dimeric in solution and tetramerizes in the unit crystal. The crystal structure of the oligomer reveals that two Hpa2 dimers are held together by interaction between the bound acetyl-CoA molecules. The average B-factor value is 23.9 (<scene name='56/564050/Bakhbone_mainechain/1' target=0>main chain</scene>) with a 25.4 <scene name='56/564050/Sidechain/2' target=0>side chain</scene>. The R-factor is 0.19. <ref name=Shiva/> Core fold features include four conserved sequence motifs of the GNAT family and comprises a central highly curved five stranded <scene name='56/564050/Beta_sheets/1' target=0>Beta sheets</scene> (β1-β5) surrounded on both sides by helical segments (α1 and α3).<ref name=Shiva/> | Has a four chain structure (A, D, C, B) with 2.4 A resolution, and 2.9 A resolution with a co-factor (acetyl-CoA). Each monomer has a similar and compact Alpha-Beta structure. The structure's core contains a central mixed five-stranded sheet structure from sheets β1 to β5. Strands β1 to β4, however, are organized in an anti-parallel arrangement while β4 and β5 are parallel, but only at their amino-terminal ends. At the other end of the parallel β4 and β5 strands, they are spread apart because of a β bulge in strand β4 caused by residue N74 of strand β3 as well as N91 and D92 of β4. The central sheet is accompanied on each side by two Alpha-helices. Helices α1 and α2 are on one side of the sheet with α1 lying nearly flat against and perpendicular to other direction of the strands, while helices α3 and α4 are on the opposite side of the sheet with helix α3 cupped within the curved face of the sheet. <ref name=Shiva/>The method used to determine the structure was [[X-ray crystallography]]. Sedimentation and crystal structure analysis clearly shows that Hpa2 is dimeric in solution and tetramerizes in the unit crystal. The crystal structure of the oligomer reveals that two Hpa2 dimers are held together by interaction between the bound acetyl-CoA molecules. The average B-factor value is 23.9 (<scene name='56/564050/Bakhbone_mainechain/1' target=0>main chain</scene>) with a 25.4 <scene name='56/564050/Sidechain/2' target=0>side chain</scene>. The R-factor is 0.19. <ref name=Shiva/> Core fold features include four conserved sequence motifs of the GNAT family and comprises a central highly curved five stranded <scene name='56/564050/Beta_sheets/1' target=0>Beta sheets</scene> (β1-β5) surrounded on both sides by helical segments (α1 and α3).<ref name=Shiva/> | ||
[[Image:Chain.jpg.png | thumb | '''Figure 1.''' Sequence of Hpa2.]] | [[Image:Chain.jpg.png | thumb | '''Figure 1.''' Sequence of Hpa2.]] | ||
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=Secondary Structure= | =Secondary Structure= | ||
Most of the secondary structure elements of the monomer contribute residues involved in dimer contacts. A large part of the interface is formed by two projections from the core part of the monomer structure. The first projection is formed by the C-terminal end of strand | Most of the secondary structure elements of the monomer contribute residues involved in dimer contacts. A large part of the interface is formed by two projections from the core part of the monomer structure. The first projection is formed by the C-terminal end of strand β3, turn β3-β4, and the N-terminal end of strand β4, while the second is formed by strand β7. Together with strands β5 and β6 they form a barrel-like structure containing ten strands in which the component strands of the barrel locked together.<ref name=Shiva> Most importantly, strand b7 from each monomer interacts between strands β5 and β6 of the opposite monomer, which also extends the central sheet structure by two strands. Also, the two projections interact with residues from helices α1 and α2, turn α1 α2, turn α2 β2, and helices α3 and α4 of the opposite monomer. There are eight beta-strands, four <scene name='56/564050/Alpha_helices/2'>Alpha-helices</scene>, and ten turns. Thirty-three percent of the secondary structure is helical (5 helices and 50 residues), while thirty-one percent consists of Beta-sheets (6 strands and 47 residues). <ref name=desperate/> | ||
[[Image:Hpa2_Active_Sites.jpg]] [[Image:Hpa2 Secondary Structure.jpg]] | [[Image:Hpa2_Active_Sites.jpg]] [[Image:Hpa2 Secondary Structure.jpg]] | ||
