Crystallization of the Altitude Adapted Hemoglobin of Guinea Pig

Abstract

Hemoglobin is the versatile oxygen carrier in the blood of vertebrates and a key factor for adaptation to live in high altitudes. Several structural changes are known to account for increased oxygen affinity in hemoglobin of altitude adapted animals such as llama and barheaded goose. Guinea pigs are adapted to live in high altitudes in the Andes and consequently their hemoglobin has an increased oxygen affinity. However, the structural changes responsible for the adaptation of guinea pig hemoglobin are unknown. Here we report the crystallization of guinea pig hemoglobin in the presence of 2.6 M ammonium sulfate and a preliminary analysis of the crystals. Crystals diffract up to a resolution of 2.0 A. They are orthorhombic with space group C 2 2 2(1) and cell dimensions a = 84.08 A, b = 90.21 A and c = 83.44 A.

Structure of the Altitude Adapted Hemoglobin of Guinea Pig in the R2-State

“…The α-chain of guinea pig hemoglobin shares 75% identical amino acids with human hemoglobin, while the β-chain is identical with its counterpart in human hemoglobin in 65% of the positions. Absorption spectroscopy of dissolved crystals indicated that guinea pig hemoglobin crystallized as met-hemoglobin [27]. The active site and its surrounding amino acids are typical in comparison with other hemoglobins in the met state.…”

“…Crystal parameters have been reported before [27]. The structure solution was obtained by molecular replacement with carbonmonoxy horse hemoglobin (PDB-code: 2D5X) as starting model, using the program PHASER implemented in the CCP4 suite [31].…”

“…We have recently reported the crystallization of the major component of guinea pig hemoglobin in the met-state and now present the first structure of guinea pig hemoglobin at 1.8 Å resolution [27].…”