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1mko

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{{STRUCTURE_1mko| PDB=1mko | SCENE= }}
{{STRUCTURE_1mko| PDB=1mko | SCENE= }}
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'''A Fourth Quaternary Structure of Human Hemoglobin A at 2.18 A Resolution'''
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===A Fourth Quaternary Structure of Human Hemoglobin A at 2.18 A Resolution===
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==Overview==
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The liganded hemoglobin (Hb) high-salt crystallization condition described by Max Perutz has generated three different crystals of human adult carbonmonoxy hemoglobin (COHbA). The first crystal is isomorphous with the "classical" liganded or R Hb structure. The second crystal reveals a new liganded Hb quaternary structure, RR2, that assumes an intermediate conformation between the R form and another liganded Hb quaternary structure, R2, which was discovered more than a decade ago. Like the R2 structure, the diagnostic R state hydrogen bond between beta2His97 and alpha1Thr38 is missing in the RR2 structure. The third crystal adopts a novel liganded Hb conformation, which we have termed R3, and it shows substantial quaternary structural differences from the R, RR2, and R2 structures. The quaternary structure differences between T and R3 are as large as those between T and R2; however, the T --&gt; R3 and T --&gt; R2 transitions are in different directions as defined by rigid-body screw rotation. Moreover, R3 represents an end state. Compared to all known liganded Hb structures, R3 shows remarkably reduced strain at the alpha-heme, reduced steric contact between the beta-heme ligand and the distal residues, smaller alpha- and beta-clefts, and reduced alpha1-alpha2 and beta1-beta2 iron-iron distances. Together, these unique structural features in R3 should make it the most relaxed and/or greatly enhance its affinity for oxygen compared to the other liganded Hbs. The current Hb structure-function relationships that are now based on T --&gt; R, T --&gt;R --&gt; R2, or T --&gt; R2 --&gt; R transitions may have to be reexamined to take into account the RR2 and R3 liganded structures.
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(as it appears on PubMed at http://www.pubmed.gov), where 15938624 is the PubMed ID number.
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{{ABSTRACT_PUBMED_15938624}}
==About this Structure==
==About this Structure==
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[[Category: Relaxed state]]
[[Category: Relaxed state]]
[[Category: Rr2 state]]
[[Category: Rr2 state]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 01:19:07 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Jul 3 00:12:07 2008''

Revision as of 21:12, 2 July 2008

Image:1mko.png

Template:STRUCTURE 1mko

A Fourth Quaternary Structure of Human Hemoglobin A at 2.18 A Resolution

Template:ABSTRACT PUBMED 15938624

About this Structure

1MKO is a Protein complex structure of sequences from Homo sapiens. Full crystallographic information is available from OCA.

Reference

The enigma of the liganded hemoglobin end state: a novel quaternary structure of human carbonmonoxy hemoglobin., Safo MK, Abraham DJ, Biochemistry. 2005 Jun 14;44(23):8347-59. PMID:15938624

Page seeded by OCA on Thu Jul 3 00:12:07 2008

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