Sandbox Reserved 774: Difference between revisions

Histone Acetyltransferase Hpa2 is a member of the GNAT (Gcn5-related N-acetyltransferases) super-family of enzymes that are found spread out across nature and use acyl-CoA's to acylate their cognate substrates.<ref name=desperate>"Histone Acetyltransferase HPA2 from Saccharomyces Cerevisiae." Protein Data Bank. EMDataBank, n.d. Web. 17 Nov. 2013.[http://www.rcsb.org/pdb/explore/explore.do?structureId=1QSO RCSB.org]</ref> GNAT is a catalytic subunit of ADA and SAGA histone acetyltransferase complexes. <ref>"GCN5/YGR252W Summary." YeastGenome.org. Standford University, n.d. Web. 26 Nov. 2013. [http://www.yeastgenome.org/cgi-bin/locus.fpl?locus=gcn5 YeastGenome.org]</ref>Hpa2 is found in the organism Saccharomyces Cerevisiae, which is more commonly known as Baker's Yeast.<ref>"Q06592 (HPA2_YEAST) Reviewed, UniProtKB/Swiss-Prot." Unitprot.org. UniProtKB, 13 Nov. 2013. Web. 16 Nov. 2013.[http://www.uniprot.org/uniprot/Q06592 UnitPro.org]</ref> It was also discovered in other organisms, such as Pelagibacterium halotolerans B2 - a marine halotolerant bacterium in the East China Sea. <ref>Huo. "Complete Genome Sequence of Pelagibacterium Halotolerans B2(T)." J. Bacteriol 197.8 (2012): 1. Web. 26 Nov. 2013. [http://www.ncbi.nlm.nih.gov/pubmed/22156395 NCBI.nlm.nih.gov]</ref> In vitro, Hpa2 serves to acetylate histone H3 'Lys-4' and 'Lys-14' and histone H4 'Lys-5' and 'Lys-12.' In solution, Hpa2 forms a dimer, and upon binding with AcCoA forms a tetramer.<ref name=desperate/><ref name=Shiva/> It is classified as a [[transferase]].<ref name=Shiva>Angus-Hill, et al. "Crystal Structure of the Histone Acetyltransferase Hpa2: a Tetrameric Member of the Gcn5-related N-acetyltransferase Superfamily." J. Mol. Biol. 1999.3338 (1999): 1-14. Web. 18 Nov. 2013.</ref>

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 B3, turn B3-B4, and the N-terminal end of strand B4, while the second is formed by strand B7. Together with strands B5 and B6 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 b5 and b6 of the opposite monomer, which also extends the central sheet structure by two strands. Also, the two projections interact with residues from helices a1 and a2, turn a1 a2, turn a2 b2, and helices a3 and a4 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=desperation/>