Structural Basis for High Affinity Volatile Anesthetic Binding in a Natural 4-helix Bundle Protein

Journal Article · Sat Jan 01 04:00:00 EST 2005 · Faseb J.

DOI:https://doi.org/10.1096/fj.04-3171com· OSTI ID:913732

Liu, R; Loll, P; Eckenhoff, R

Physiologic sites for inhaled anesthetics are presumed to be cavities within transmembrane 4-{alpha}-helix bundles of neurotransmitter receptors, but confirmation of binding and structural detail of such sites remains elusive. To provide such detail, we screened soluble proteins containing this structural motif, and found only one that exhibited evidence of strong anesthetic binding. Ferritin is a 24-mer of 4-{alpha}-helix bundles; both halothane and isoflurane bind with K{sub A} values of {approx}10{sup 5} M{sup -1, } higher than any previously reported inhaled anesthetic-protein interaction. The crystal structures of the halothane/apoferritin and isoflurane/apoferritin complexes were determined at 1.75 Angstroms resolution, revealing a common anesthetic binding pocket within an interhelical dimerization interface. The high affinity is explained by several weak polar contacts and an optimal host/guest packing relationship. Neither the acidic protons nor ether oxygen of the anesthetics contribute to the binding interaction. Compared with unliganded apoferritin, the anesthetic produced no detectable alteration of structure or B factors. The remarkably high affinity of the anesthetic/apoferritin complex implies greater selectivity of protein sites than previously thought, and suggests that direct protein actions may underlie effects at lower than surgical levels of anesthetic, including loss of awareness.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 913732
• Report Number(s): BNL--78300-2007-JA
• Journal Information: Faseb J., Journal Name: Faseb J. Vol. 19; ISSN FAJOEC; ISSN 0892-6638
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AFFINITY
ANESTHETICS
CAVITIES
CRYSTAL STRUCTURE
DIMERIZATION
ETHERS
FERRITIN
OXYGEN
PROTEINS
PROTONS
RESOLUTION
national synchrotron light source