View source for 1aqh

[[Image:1aqh.gif|left|200px]]<br /><applet load="1aqh" size="450" color="white" frame="true" align="right" spinBox="true" 
caption="1aqh, resolution 2.00&Aring;" />
'''ALPHA-AMYLASE FROM ALTEROMONAS HALOPLANCTIS'''<br />

==Overview==
Alteromonas haloplanctis is a bacterium that flourishes in Antarctic, sea-water and it is considered as an extreme psychrophile. We have, determined the crystal structures of the alpha-amylase (AHA) secreted by, this bacterium, in its native state to 2.0 angstroms resolution as well as, in complex with Tris to 1.85 angstroms resolution. The structure of AHA, which is the first experimentally determined three-dimensional structure, of a psychrophilic enzyme, resembles those of other known alpha-amylases, of various origins with a surprisingly greatest similarity to mammalian, alpha-amylases. AHA contains a chloride ion which activates the hydrolytic, cleavage of substrate alpha-1,4-glycosidic bonds. The chloride binding, site is situated approximately 5 angstroms from the active site which is, characterized by a triad of acid residues (Asp 174, Glu 200, Asp 264)., These are all involved in firm binding of the Tris moiety. A reaction, mechanism for substrate hydrolysis is proposed on the basis of the Tris, inhibitor binding and the chloride activation. A trio of residues (Ser, 303, His 337, Glu 19) having a striking spatial resemblance with, serine-protease like catalytic triads was found approximately 22 angstroms, from the active site. We found that this triad is equally present in other, chloride dependent alpha-amylases, and suggest that it could be, responsible for autoproteolytic events observed in solution for this cold, adapted alpha-amylase.

==About this Structure==
1AQH is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Pseudoalteromonas_haloplanktis Pseudoalteromonas haloplanktis] with CA and CL as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Alpha-amylase Alpha-amylase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.1 3.2.1.1] Known structural/functional Sites: <scene name='pdbsite=AVE:Active Site'>AVE</scene>, <scene name='pdbsite=CDE:Chloride Is An Activator For This Enzyme'>CDE</scene> and <scene name='pdbsite=CUM:Ca'>CUM</scene>. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1AQH OCA]. 

==Reference==
Crystal structures of the psychrophilic alpha-amylase from Alteromonas haloplanctis in its native form and complexed with an inhibitor., Aghajari N, Feller G, Gerday C, Haser R, Protein Sci. 1998 Mar;7(3):564-72. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=9541387 9541387]
[[Category: Alpha-amylase]]
[[Category: Pseudoalteromonas haloplanktis]]
[[Category: Single protein]]
[[Category: Aghajari, N.]]
[[Category: Haser, R.]]
[[Category: CA]]
[[Category: CL]]
[[Category: 4-glucan-4-glucanohydrolase]]
[[Category: alpha-1]]
[[Category: alpha-amylase]]
[[Category: beta-alpha-eight barrel]]
[[Category: hydrolase]]
[[Category: psychrophilic enzyme]]

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