Sandbox Reserved 774: Difference between revisions

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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 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/>
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]]
 
=Mechanism=
 
Protein surfaces near the active site are characterized by a positive electrostatic potential.<ref name=Akhlaghi>Vetting, et al. "Structure and Functions of the GNAT Superfamily of Acetyltransferases." Arch Biochem Biophys 433(2004): Web. 26 Nov. 2013.</ref> In each structure there are several multi-chain carbonyl groups without hydrogen bonding partners in the active site. These could act in a proton transfer pathway by helping locate water molecules. Around the acetyl group, there exists a hydrophobic pocket which would stabilize the neutral charge while the substrate is bound to the enzyme once the amino group is deprotonated.
 


=Mechanism=
=Mechanism=