The three-dimensional crystal structure of bovine trypsinogen at approximately pH 7.5 was initially solved at 2.6 A resolution using the multiple isomorphous replacement method. Preliminary refinement cycles of the atomic coordinates trypsinogen have been carried out first to a resolution of 2.1 A, and later to 1.9 A, using constrained difference Fourier refinement; During the process, structure factors Fc and phi c were calculated from the trypsinogen structure and final interpretation was based on an electron-density map computed with terms (2 Fo - Fc) and phases phic at a resolution of 1.9 A. Crystals of trypsinogen grown from ethanol-water mixtures are trigonal with space group P3121, and cell dimension a = 55.17 A and c = 109.25 A. The structure is compared with the bovine diisopropylphosphoryltrypsin structure at approximately pH 7.2, oirginally determined from orthohombic crystals by Stroud et al. (Stroud, R.M., Kay L.M., and Dickerson, R.E. (1971), Cold Spring Harbor Symp. Quant. Biol. 36, 125-140; Stroud, R.M., Kay, L.M., and Dickerson, R.E. (1974), J. Mol. Biol. 83, 185-208), and later refined at 1.5 A resolution by Chambers and Stroud (Chambers, J.L., and Stroud, R.M. (1976), Acta Crystallogr. (in press)). At lower pH, 4.0-5.5 diogen, with cell dimensions a = 55.05 A and c = 109.45 A. This finding was used in the solution of the six trypsinogen heavy-atom derivatives prior to isomorphous phase analysis, and as a further basis of comparison between trypsinogen and the low pH trypsin structure. There are small differences between the two diisopropylphosphoryltrypsin structures. Bovine trypsinogen has a large and accessible cavity at the site where the native enzyme binds specific side chains of a substrate. The conformation and stability of the binding site differ from that found in trypsin at approximately pH 7.5, and from that in the low pH form of diisopropylphosphoryltrypsin. The catalytic site containing Asp-102, His-57, and Ser-195 is similar to that found in trypsin and contains a similar hydrogen-bounded network. The carboxyl group of Asp-194, which is salt bridged to the amino terminal of Ile-16 in native trypsin or other serine proteases, is apparently hydrogen bonded to internal solvent molecules in a loosely organized part of the zymogen structure. The unusually charged N-terminal hexapeptide of trypsinogen, whose removal leads to activation of the zymogen, lies on the outside surface of the molecule. There are significant structural changes which accompany activation in neighboring regions, which include residues 142-152, 215-550, 188A-195. The NH group of Gly-193, normally involved in stabilization of reaction intermediates (Steitz, T.A., Henderson, R., and Blow, D.M. (1969), J. Mol. Biol. 46, 337-348; Henderson, R. (1970), J. Mol. Biol. 54, 341-354; robertus, J.D., Kraut, J., Alden, R.A., and Birkoft, J.J. (1972), Biochemistry 11, 4293-4303) in the enzyme, is moved 1.9 A away from its position in trypsin...

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The beta-gene-cluster haplotype and alpha-gene status were determined for 221 patients with sickle cell anemia, 41 with SC disease, and 21 with S-beta-thalassemia. Among SS patients, eleven beta S haplotypes were found in 21 combinations. Three haplotypes--the Benin (Ben) [---+-], the Central African Republic (CAR) [+---+], and the Senegal (Sen) [+- ]--comprise 61%, 21%, and 10% of the chromosomes, respectively. Cleavage at the Xmn I site 5' to the G gamma gene was observed only when the Senegalese arrangement was present. The linear correlation which exists between the absolute value of the G gamma chains and the Hb F for each haplotype combination suggests a feed-back mechanism which controls the G gamma to A gamma ratio and thus the Hb F level (or vice versa). The A gamma T chain was present with specific haplotypes [++-++] and [++-+-]. Heterozygous or homozygous alpha-thalassemia-2 was present in 36% of the SS patients and was randomly distributed among beta S-gene-cluster haplotypes. The variable levels of hemoglobin, MCV, Hb F, G gamma chains, and Hb A2 are in response to the heterogeneous genetic mix of the beta S-gene-cluster haplotypes and alpha-thalassemia-2 in American patients with sickle cell anemia. The influence of alpha-thalassemia-2 on the level of Hb F is dependent on the beta S-cluster haplotype. Hb A2 levels increased with decrease in the number of alpha genes. Among SC and S-beta-thalassemia patients the beta-cluster polymorphisms on the beta S chromosome were those commonly associated with the African origins of beta S haplotype. The haplotype [+--+-] was present on the C chromosome in 90% of the cases. Most beta-thalassemia chromosomes had haplotypes that matched the common African polymorphisms. An alpha-gene deletion was found in 29% of the SC and S-beta-thalassemia patients.

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The peptides in partial acidic and basic hydrolysates of gelatin have been separated initially by chromatographing on the ion exchanger Dowex-50, and then further resolved by chromatographing in the form of the DNP-peptides on silicic acid-Celite. In this manner, 34 peptides (mainly dipeptides) have been isolated, identified and quantitatively estimated. These peptides account for a minimum of 42% of the threonine, 27% of the serine, 22%. of the proline, 13% of the hydroxyprolinc and 20% of the glycine and alanine in gelatin. The nature and quantity of the peptides which have been isolated from gelatin in this study as well as those which other investigators have identified do not support the assumption that the structure of collagen and gelatin may be described by the repetitive sequence -P-G-Rin which P represents prolyl or hydroxyprolyl, G glycyl and R other amino acid residues, The analytical data provide some evidence that the sequence -gly-pro-hypro-gly-(or similar sequence) may be of frequent occurrence in gelatin and collagen.