Identification of pre-gamma-globin

Detection of protein glutathionylation

Recent studies indicate that protein glutathionylation is an important regulatory mechanism. The develop-ment of redox proteomics techniques to identify proteins undergoing glutathionylation has a key role in defining the importance of this post-translational modification, although the available methods are not yet comparable to those for the study of other modifications like phosphorylation. We describe here methods that have been successfully employed to identify in vitro glutathionylated proteins.

Humans and old world monkeys have similar patterns of fetal globin expression

The expression of epsilon- and gamma-globin mRNA and protein has been determined in three Old World monkey species (Macaca mulatta, Macaca nemestrina, and Cercopithecus aethiops). Using RT-PCR with primers for epsilon- and gamma-globin, both mRNAs were detected in early fetal stages, whereas at 128 days (85% of full term), only gamma was expressed. High-performance liquid chromatography was used for separation and quantitation, and matrix-assisted laser desorption/ionization mass spectrometry was used for identification of globin polypeptides. An alpha-globin polymorphism was observed in all of the species examined. During fetal life, gamma-globin was the predominant expressed beta-type globin. The red blood cells of infants still contained substantial amounts of gamma-globin, which declined to negligible levels in 14 weeks as beta-globin expression reached adult values. The ratio of gamma1- to gamma2-globins (equivalent to Ggamma/Agamma in humans) was approximately 2.5, similar to the Ggamma/Agamma ratio observed in humans. Thus, gamma-globin gene expression in these Old World monkeys species has three features in common with human expression: expression of both duplicated gamma genes, the relative preponderance of gamma1 over gamma2 expression, and the delay of the switch from gamma- to beta-globin until the perinatal period. Thus, the catarrhines seem to share a common pattern of developmental switching in the beta-globin gene cluster, which is distinct from the timing of expression in either prosimians or the New World monkeys. Our results indicate that an Old World monkey, such as Rhesus, could serve as a model organism (resembling humans) for experimentally investigating globin gene expression patterns during the embryonic, fetal, and postnatal stages.

Characterization of the embryonic globin chains of the marsupial Tammar wallaby, Macropus eugenii

The embryonic hemoglobins of the marsupial Tammar wallaby (Macropus eugenii) are known to aggregate, which was shown by the finding that the Hill coefficient, h, was greater than 4.0 in the upper part of the oxygen equilibrium curve. Here, we have undertaken a detailed primary structure analysis of the Tammar wallaby pouch young hemoglobin complement, which we hoped might provide clues into the residues that cause aggregation and a high embryonic h. The Tammar wallaby embryonic hemoglobin complement is principally four major hemoglobins each with a different isoelectric point. Two early expressed hemoglobins contain the same embryonic beta-like chain, epsilon (epsilon), but two separate alpha-like chains, termed zeta and zeta prime (zeta and zeta') both of which are N-terminally blocked. The later two expressed hemoglobins contain the same adult alpha-chain, but different beta-like chains. The latest expressed hemoglobin contains the same beta-like chain, epsilon, as the two early expressed forms, but the third expressed hemoglobin contains a unique beta-like chain which we have termed omega (omega). A protein database similarity search using the first 54 N-terminal amino acids of the omega-chain showed a range of sequence identities of 57-72% to all known mammalian beta-like chains, including the other marsupial epsilon-chains. The closest identity, reflected by both the highest percentage identity and Smith-Waterman score, was with the embryonic beta-chains of the aves. While the primary structures of the hemoglobins reported here do not explain the low hemoglobin-oxygen affinity in embryonic marsupial blood, the finding of the similarity with the bird globin-like sequence with one of the marsupial chains has implications on mammalian globin evolution. How many other marsupials and placental mammals are harboring a bird-like globin in their embryos?