Isolation and characterization of the hemoglobin from the lanceolate fluke Dicrocoelium dendriticum

The hemoglobin of the flatworm Dicrocoelium dendriticum, a lanceolate fluke which infests the hepatic ducts of certain mammals, has been isolated by gel filtration and ion-exchange chromatography. The molecular weight of the denatured protein was found to be 15500, a value in the same range as hemoglobin subunits. The fact that the native hemoglobin has an apparent molecular weight of 22000 in 0.01 M phosphate buffer, pH 7.4, suggests limited aggregation. The protein contains, as all other myoglobins and hemoglobins, one molecule of non-covalently associated ferroprotoporphyrin IX per polypeptide chain. It forms the same ligand derivatives with very similar spectral properties as vertebrate hemoglobins. The high oxygen affinity (p50 is 0.07--0.1 mmHg or 9.3--13.3 Pa at 20 degrees C and pH 7.0) and the absence of heme-heme interaction of (Hill coefficient nH=1.0) are properties which this heme protein shares with other monomeric hemoglobins from invertebrate and lower vertebrate organisms. The native hemoglobin exists in two forms, having isoelectric points of 4.51 and 4.53, which do not differ in their amino-acid compositions. Dansylation indicated that the amino-terminal amino-acid residue is alanine. The carboxy-terminal sequence, determined by carboxypeptidase A digestion of the globin, is -His-Ala-Leu.

Revised amino acid sequence of Qbeta coat protein between positions 1 and 60

A reinvestigation of the primary structure of Qbeta coat protein between positions 1 and 60 was undertaken to resolve two discrepancies between the published amino acid seuqence (Maita, T., and Konigsberg, W. (1971) J. Biol. Chem. 246, 5003-5024) and the cognate nucleotide sequence recently determined in our laboratory (C. Escarmis and M. A. Billeter, unpublished results). The 22nd amino acid was asparagine rather than aspartic acid, and an additional amino acid, serine, was present between proline in position 55 and arginine in position 56. The revised structure agrees with the nucleotide sequence determined so far.

Heat loss from feet of herring gulls at rest and during flight

The role of the feet of herring gulls (Larus argentatus) in heat dissipation was estimated during rest and wind-tunnel flight. We determined the blood flow to the feet and the arteriovenous temperature difference and thus estimated heat loss from the feet. Determinations of oxygen consumption and respiratory water loss at rest gave a heat production of about 8 W; 37-56% of this heat was lost from the feet (air temp = 10-35 degrees C). During flight heat production was estimated to be about 57 W and heat loss from the feet was 46 W, about 80% of the heat production in flight. Thus the webbed feet are an important avenue of heat loss in the herring gull.

Affinity labeling of the primary bilirubin binding site of human serum albumin

A label for the bilirubin binding sites of human serum albumin was synthesized by reacting 2 mol of Woodward's reagent K (N-ethyl-5-phenylisoxazolium-3'-sulfonate) with 1 mol of bilirubin. This yielded a water-soluble derivative in which both carboxyl groups of bilirubin were converted to reactive enol esters. Covalent labeling was achieved by reacting the label with human serum albumin under nitrogen at pH 9.4 and 20 degrees. Under the same conditions, no covalent binding to the monomers of several proteins could be demonstrated. The number of binding sites for bilirubin and the label were found to be the same, and competition experiments with bilirubin showed inhibition of covalent labeling. The absorption, fluorescence and CD spectra of the label in a complex with human serum albumin were similar to those of the bilirubin human serum albumin complex. However, following covalent attachment to the spectral properties were changed, indicating loss of conformational freedom of the chromophore. Labeling ratios were selected to result in the incorporation of less than 1 mol of label/mol of human serum albumin. Under these conditions, labeling is thought to occur primarily at the high affinity binding site.

Dihydrofolate reductase from bovine liver. Enzymatic and structural properties

Dihydrofolate reductase from bovine liver has been purified 5000-fold employing conventional techniques and methotrexate/aminohexyl/Sepharose affinity chromatography. Electrophoresis of the isolated enzyme on polyacrylamide gels resulted in the separation of two enzymatically active protein components which were not interconvertible by treatment with dihydrofolate and/or the coenzyme. The two forms, present in a ratio of 20:1, were found by isoelectric focusing to have isoelectric points of 7.15 and 5.94. They had identical specific activities toward dihydrofolate (26.1-27.0 U/mg) and folate (1.3-2.2 U/mg), and had identical molecular weights (23500) and amino acid compositions. Due to the small quantity of the acidic form and the similarity of the two forms, the amino-terminal sequence (19 residues) was determined on a mixture of carboxymethylated reductase. The single sulfhydryl group of the enzyme can be modified by several sulfhydryl reagents in the native enzyme without loss of activity. Modification of the same residue occurs in the denaturated state and partially inhibits renaturation to the fully acitve enzyme. One disulfide bridge was detected by reduction and alkylation. The cleavage of this bond did not effect the enzymatic activity.

The amino-acid sequence of a peptide (PS-1) from Drosophila funebris: a paragonial peptide from males which reduces the receptivity of the female

The substance, PS-1, produced in the paragonial gland of adult male Drosophila funebris influences the mating behavior of virgin female flies after injection. The substance was isolated and characterized as a 27-residue peptide. The complete amino acid sequence was determined by manual sequence analysis of tryptic peptides, automated Edman degradation, and carboxypeptidase A digestion. The sequence is Asp-Val/Leu-Pro-Ser-Ala-Asn-Ala-Asn-Ala-Asn-Gln-Arg-Thr-Ala-Ala-Ala-Lys-Pro-Gln-Ala-Asn-Ala-Glu-Ala-Ser-Ser. The ratio of Val : Leu in the second position of the sequence is 7:3. This is the first detailed report on an insect peptide which causes a biological response in the opposite sex following mating.