Primary structure of the major β-chain of rat haemoglobins

The amino acid sequence of the major β-chain, ^IIβ, from rat haemoglobins was established with an automated sequencer. Amino acid heterogeneities were found that appear to result from allelic variation at particular residues. We applied several new or unusual techniques in determining the sequence: (1) reaction of the polypeptide with dansylaziridine for detection of cysteine; (2) blockage of the N-terminal residue and the ε-amino group of lysine residues with 1-fluoro-2-nitro-4-trimethylammoniobenzene iodide and subsequent identification of the modified lysine phenylthiohydantoin by absorbance at 420nm; (3) identification of histidine phenylthiohydantoin by its blue fluorescence under long-wave u.v. light; (4) cleavage of the chain into two or three fragments and subsequent sequencing without purification [a detailed statement giving the major phenylthiohydantoins assigned at each step for each sequence run before their alignment in individual sequences has been deposited as Supplementary Publication SUP 50084 (10 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1978) 169, 5]; (5) separation of fragments produced by CNBr cleavage by cation-exchange chromatography; (6) peptide sequencing after attachment of the peptide to cytochrome c. The amino acid sequence was confirmed by amino acid compositions of the complete chain, of CNBr fragments 1 and 3, and of 11 purified tryptic peptides.     

Testing with puromycin for amino acyl trnas that limit the rate of peptide chain extension

Summary With puromycin one can recognize when the synthesis of a given protein is dependent on amino acyl tRNA that is present in rate limiting amount. We demonstrate this use of puromycin by its interaction with another inhibitor, L-o-methylthreonine. L-o-methylthreonine lowers the Ile-tRNA concentration in the cell, thereby inhibiting synthesis of proteins containing isoleucine. In certain rabbits, the a hemoglobin chain has three isoleucyl residues and the chain none. L-o-methylthreonine thus inhibits globin synthesis in intact reticulocytes from these rabbits. When puromycin and L-o-methylthreonine are used together, the two inhibitors synergize in inhibiting a globin synthesis. Hence, puromycin is a more effective inhibitor when the Ile-tRNA concentration is lowered. Cycloheximide and sodium fluoride have different modes of action from puromycin. Neither synergizes with L-o-methylthreonine; instead, the interaction is less than additive. We have found that chain synthesis in rabbit reticulocytes is more sensitive than to inhibition by puromycin. This difference could reflect either differences in amino acid sequence or tRNA dependent limitations of chain elongation. The switch from fetal to adult hemoglobin in humans does not involve changes in limiting amino acyl tRNA because, for cord blood from infants of different developmental ages, the puromycin sensitivity of incorporation into and chains remains constant.     

Structural analysis of the minor human hemoglobin components: Hb AIa1, Hb AIa2 and Hb AIb

Human hemolysate contains several minor hemoglobin components, including Hb AIa1, Hb AIa2, Hb AIb and Hb AIc which are post-translational modifications of the major component, Hb A0. Hb AIc is known to contain glucose attached to the N terminus of the beta chains by a ketoamine linkage. We separated the alpha and beta globin chains from purified Hb AIa1, Hb AIa2 and Hb AIb by ion-exchange chromatography. The beta chains were reducible by sodium borohydride and gave a positive thiobarbituric acid test. These results indicated that they are modified by ketoamine-linked carbohydrate. In addition, phosphate analysis revealed 1.5 phosphate residue associated with each beta AIa1 chain and 1 phosphate residue with each beta AIa2 chain. Hb AIa1, Hb AIa2 and Hb AIb were all found to be contaminated by non-globin proteins. Protein-sequencing approaches demonstrated that the N termini of beta AIa1, beta AIa2 and beta AIb were blocked. In support of this conclusion, analysis of tryptic digests of beta AIa2 and B AIb revealed modified N-terminal peptides. We conclude that, like Hb AIc, components Hb AIa1, Hb AIa2 and Hb AIb also contain a sugar moiety linked to the N terminus of the beta chain.     

Loss of rapid transferrin receptor recycling due to a mutation in Sec15l1 in hbd mice

The hbd (hemoglobin deficit) mutation affects iron trafficking in murine reticulocytes. It is due to a deletion that eliminates exon 8 of Sec15l1, the homolog of a gene that encodes an exocyst component in yeast. We tested the hypothesis that the mutation causes defective slow or rapid receptor recycling by measuring endocytosis and exocytosis of transferrin by hbd reticulocytes. Endocytosis and initial iron incorporation were relatively unaffected, but exocytosis was unexpectedly slowed. These data indicate that rapid transferrin recycling is defective after pSec15l1 has mutated.     

Catchments catch all: long-term population history of a giant springtail from the southeast Australian highlands--a multigene approach

Phylogeography can reveal evolutionary processes driving natural genetic-geographical patterns in biota, providing an empirical framework for optimizing conservation strategies. The long-term population history of a rotting-log-adapted giant springtail (Collembola) from montane southeast Australia was inferred via joint analysis of mitochondrial and multiple nuclear gene genealogies. Contemporary populations were identified using multilocus nuclear genotype clustering. Very fine-scale sampling combined with nested clade and coalescent-based analyses of sequences from mitochondrial cytochrome oxidase I and three unlinked nuclear loci uncovered marked population structure, deep molecular divergences, and abrupt phylogeographical breaks over distances on the order of tens of kilometres or less. Despite adaptations that confer low mobility, rare long-distance gene flow was implicated: novel computer simulations that jointly modelled stochasticity inherent in coalescent processes and that of DNA sequence evolution showed that incomplete lineage sorting alone was unable to explain the observed spatial-genetic patterns. Impacts of Pleistocene or earlier climatic cycles were detected on multiple timescales, and at least three putative moist forest refuges were identified. Water catchment divisions predict phylogeographical patterning and present-day population structure with high precision, and may serve as an excellent surrogate for biodiversity indication in sedentary arthropods from topographically heterogeneous montane temperate forests.     

The design and SAR of a novel series of 2-aminopyridine based LRRK2 inhibitors

Leucine-rich repeat kinase 2 (LRRK2) has attracted considerable interest as a therapeutic target for the treatment of Parkinson’s disease. Compounds derived from a 2-aminopyridine screening hit were optimised using a LRRK2 homology model based on mixed lineage kinase 1 (MLK1), such that a 2-aminopyridine-based lead molecule 45, with in vivo activity, was identified.     

Thyrotropin-releasing hormone (TRH) acts centrally to stimulate gastric contractility in rats

Changes in gastric contractility induced by intracisternal (ic) injection of thyrotropin-releasing hormone (TRH) or a stable TRH analog, RX77368 [p-Glu-His-(3,3'-dimethyl)-Pro NH2] were investigated in 24 h fasted-conscious rats. Gastric contractility was monitored using chronically implanted extraluminal force transducers sutured to the corpus. Response elicited by a standard meal was used as a physiologic standard. Intracisternal injection of TRH (1 microgram) or RX77368 (100 ng), unlike saline, stimulated high amplitude gastric contractions. The stimulation of gastric contractions induced by ic RX77368 was dose dependent (3-100 ng), rapid in onset, long lasting and not mimicked by the intravenous route of administration. Atropine (0.1 mg/kg) partially antagonized and vagotomy totally blocked the RX77368 (100 ng, ic)-induced stimulation of gastric contractility. These results demonstrated that TRH or RX77368 acts within the brain to elicit potent contractions of the stomach; TRH action appears vagally mediated probably through cholinergic mechanism.     

The anemia-induced reversible switch from hemoglobin A to hemoglobin C in caprine ruminants: immunochemical evidence that both hemoglobins are found in the same cell

During anemic episodes, goats and certain sheep replace hemoglobin A (HbA = α₂β₂^A) with hemoglobin C (HbC = α₂β₂^C). Rabbit serum directed against either purified sheep HbA or purified sheep HbC was prepared. Both types were used to test whether the two hemoglobins are found in the same cell during switching by an indirect fluorescent antibody assay.Unabsorbed antisheep HbA cross-reacted extensively with goat HbA but to a lesser extent with goat or sheep HbC. Similarly, unabsorbed antisheep HbC reacted with these antigens in the order: Sheep HbC > goat HbC > sheep HbA > goat HbA. Cross-absorption resulted in sera specific either for sheep and goat HbA or for sheep and goat HbC. The specificities were confirmed by indirect fluorescent antibody staining of sheep and goat erythrocytes containing either at least 99% HbA or at least 99% HbC.Smears of erythrocytes from sheep and goats in the process of switching were reacted with one of the absorbed sera then with fluorescein conjugated antirabbit immunoglobulin G. The sum of the fractions stained both by anti-HbA and by anti-HbC exceeded 100% during the switch. Most strikingly when HbA was replacing HbC, nearly all cells stained for HbC while more than half stained for HbA. Thus, the two hemoglobins are found in the same cell during switching.