Some effects of post-translational N-terminal acetylation of the human embryonic zeta globin protein.
Using site-directed mutagenesis we have produced the first mutant form of a human embryonic haemoglobin. We have mutated the N-terminal Ser residue of the zeta-chain of haemoglobin Portland, zeta 2 gamma 2, (which is normally acetylated) to a Val (which possesses a free amine terminus). The protein spontaneously assembles into a fully functional tetramer which shows cooperative oxygen binding. Determination of the reactivity of the mutant protein with 2,3-diphosphoglycerate indicates that the mutation process does not lead to any major disruption of the protein structure. A comparison of the properties of the mutant and wild-type proteins identifies a significant role for the normal N-terminal acetylation of the zeta-chain with regard to the alkaline Bohr effect and the sensitivity of the oxygen affinity of the protein towards chloride ions. The possible physiological significance of this modification is discussed.
Scheepens
A
A
Biochemistry and Molecular Biology Research Group, School of Biological Sciences, University of Auckland, New Zealand.
Mould
R
R
Hofmann
O
O
Brittain
T
T
D019794:2,3-Diphosphoglycerate; D000107:Acetylation; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D004163:Diphosphoglyceric Acids / Q000378:metabolism / Q000494:pharmacology; D004622:Embryo, Mammalian; D005914:Globins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism*; D006455:Hemoglobins, Abnormal / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D016297:Mutagenesis, Site-Directed; D010100:Oxygen / Q000097:blood; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D013816:Thermodynamics
D004163:Diphosphoglyceric Acids; D006454:Hemoglobins; D006455:Hemoglobins, Abnormal; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D019794:2,3-Diphosphoglycerate; C030447:hemoglobin Portland; D005914:Globins; D010100:Oxygen