Sandbox Reserved 772: Difference between revisions
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HDH functions as a homodimer, but it consists of two monomers. The presence of Zn2+ cation is required per monomer. Each HDH monomer is made of four domains, two larger domains and two smaller domains. The two larger domains make up the globule and the two smaller domains make up the extending tail. The intertwined dimer is thought to result from domain swapping. The two domains presents a similar incomplete Rossmann fold, which suggests an ancient event of gene duplication. Residues from both monomers form the active site. The active site (residue His-327) participates in acid-base catalysis <ref name="pnas">http://www.pnas.org.prox.lib.ncsu.edu/content/99/4/1859.full.pdf</ref> | HDH functions as a homodimer, but it consists of two monomers. The presence of Zn2+ cation is required per monomer. Each HDH monomer is made of four domains, two larger domains and two smaller domains. The two larger domains make up the globule and the two smaller domains make up the extending tail. The intertwined dimer is thought to result from domain swapping. The two domains presents a similar incomplete Rossmann fold, which suggests an ancient event of gene duplication. Residues from both monomers form the active site. The active site (residue His-327) participates in acid-base catalysis <ref name="pnas">http://www.pnas.org.prox.lib.ncsu.edu/content/99/4/1859.full.pdf</ref> | ||
[[ | '''Related Structures''': [http://proteopedia.org/wiki/index.php/1kae 1KAE] and [http://proteopedia.org/wiki/index.php/1kar 1KAR] | ||
[[Image:Monomer.gif |300px]]<ref name="pnas">http://www.pnas.org.prox.lib.ncsu.edu/content/99/4/1859.full.pdf</ref> | |||
'''Figure 1.''' ''(A) Stereo view of the monomer. Domains: 1, blue; 2, green; 3, orange; 4, magenta. L-histidinol, NAD, and the Zn2� are shown as ball-and-sticks. ( B) Domain 1. Rossmann fold shown in blue, V-shaped pairs of helices (residues 25 –103) connected by a linker that forms the sixth strand are in cyan. (C) Domain 2. Rossmann fold (green) in similar orientation as B. Strand-helix hairpin completes the �-sheet (residues 1–24, magenta). (D) Topology diagram. Secondary structure elements are numbered consecutively. The chain meanders between domains in the order 2 –1-3–1-2–1-3– 4. (E) HisD dimer with one molecule colored as in A and the other shown in pale colors. Zn2� atoms and NAD bound to each monomer (red) define the position of the active site.'' | |||
'''Sequence of HDH''' <ref name="structure">http://www.rcsb.org/pdb/explore/remediatedSequence.do?structureId=1K75&bionumber=1</ref> | '''Sequence of HDH''' <ref name="structure">http://www.rcsb.org/pdb/explore/remediatedSequence.do?structureId=1K75&bionumber=1</ref> | ||
[[Image:403px-Histidine decarboxylase seq.png |300px]] | [[Image:403px-Histidine decarboxylase seq.png |300px]] | ||
'''Figure. 2''' ''This is the full sequence of histidinol dehydrogenase.'' | |||
==Enzymatic Mechanism== | ==Enzymatic Mechanism== | ||
[[Image:pathways.jpg]] | [[Image:pathways.jpg]] | ||
This bifunctional enzyme converts L-histidinol to L-histidine through a L-histidinaldehyde intermediate. His-327 and Glu-326 are the two main active sites of HDH.<ref name="info">http://www.uniprot.org/uniprot/P06988#section_terms</ref> | '''Figure 3.''' ''This bifunctional enzyme converts L-histidinol to L-histidine through a L-histidinaldehyde intermediate. His-327 and Glu-326 are the two main active sites of HDH.<ref name="info">http://www.uniprot.org/uniprot/P06988#section_terms</ref>'' | ||
The reaction above is as follows: | The reaction above is as follows: | ||