Determination of polypeptide

W. Braun, C. Bosch, L. R. Brown. N. Go, and K. Wiithrich, Biochim. Biophys. Acta, 667, 377 (1981). Combined Use of Proton-Proton Overhauser Enhancements and a Distance Geometry Algorithm for Determination of Polypeptide Conformations. 

A. DiNola, H. J. C. Berendsen, and O. Edholm, Macromolecules, 17, 2044 (1984). Free Energy Determination of Polypeptide Conformations Generated by Molecular Dynamics. 

M. Billeter, T. F. Havel, and K. Wiithrich,/. Comput. Chem., 8(2), 132(1987). The Ellipsoid Algorithm as a Method for the Determination of Polypeptide Conformations from Experimental Distance Constraints and Energy Minimization. 

K. Tatemoto, V. Mutt, Isolation and characterization of the intestinal porcine PHI (PHI-27), a new member of the glucagon-secretin family. Proc. Natl. Acad. Sci. USA 78 6603-6607 (1981) K. Tatemoto, V. Mutt, Chemical determination of polypeptide hormones. Proc. Natl. Acad. Sci. USA 75, 4115-4119 (1978)... 

D.W. Urry and M.M. Long, Conformations of the Repeat Peptides of Elastin in Solution An Application of Proton and Carbon-13 Magnetic Resonance to the Determination of Polypeptide Secondary Structure. CRC Crit Rev. Biochemistry, 4,1-45,1976. 

J Moult, MNG James. An algorithm for determining the conformation of polypeptide segments m proteins by systematic search. Proteins 1 146-163, 1986. 

Carboxypeptidases are zinc-containing enzymes that catalyze the hydrolysis of polypeptides at the C-terminal peptide bond. The bovine enzyme form A is a monomeric protein comprising 307 amino acid residues. The structure was determined in the laboratory of William Lipscomb, Harvard University, in 1970 and later refined to 1.5 A resolution. Biochemical and x-ray studies have shown that the zinc atom is essential for catalysis by binding to the carbonyl oxygen of the substrate. This binding weakens the C =0 bond by... 

Determining the Amino Acid Sequence Nature of Amino Acid Sequences Synthe.sis of Polypeptides in the Laboratory... 

Later we return to an analysis of the 1° structure of proteins and the methodology used in determining the amino acid sequence of polypeptide chains, but let s first consider the extraordinary variety and functional diversity of these most interesting macromolecules. 

ENZYMATIC ANALYSIS WITH CARBOXYPEPTIDASES. Carboxypeptidases are enzymes that cleave amino acid residues from the C-termini of polypeptides in a successive fashion. Four carboxypeptidases are in general use A, B, C, and Y. Carboxypeptidase A (from bovine pancreas) works well in hydrolyzing the C-terminal peptide bond of all residues except proline, arginine, and lysine. The analogous enzyme from hog pancreas, carboxypeptidase B, is effective only when Arg or Lys are the C-terminal residues. Thus, a mixture of carboxypeptidases A and B liberates any C-terminal amino acid except proline. Carboxypeptidase C from citrus leaves and carboxypeptidase Y from yeast act on any C-terminal residue. Because the nature of the amino acid residue at the end often determines the rate at which it is cleaved and because these enzymes remove residues successively, care must be taken in interpreting results. Carboxypeptidase Y cleavage has been adapted to an automated protocol analogous to that used in Edman sequenators. 

Miao M, Cirulis JT, Lee S et al (2005) Structural determinants of cross- linking and hydrophobic domains for self-assembly of elastin-like polypeptides. Biochemistry 44 14367-14375... 

TABLE 1 Effective Length and Compressibihty Modnlns of Polypeptide Bmshes Determined by SPA in Water... 

While hydrolysis is a thermodynamically favored reaction, the amide and phosphoester bonds of polypeptides and ohgonucleotides are stable in the aqueous environment of the cell. This seemingly paradoxic behavior reflects the fact that the thermodynamics governing the equihbrium of a reaction do not determine the rate at which it will take place. In the cell, protein catalysts called enzymes are used to accelerate the rate... 

Mature human albumin consists of one polypeptide chain of 585 amino acids and contains 17 disulfide bonds. By the use of proteases, albumin can be subdivided into three domains, which have different functions. Albumin has an ellipsoidal shape, which means that it does not increase the viscosity of the plasma as much as an elongated molecule such as fibrinogen does. Because of its relatively low molecular mass (about 69 kDa) and high concentration, albumin is thought to be responsible for 75-80% of the osmotic pressure of human plasma. Electrophoretic smdies have shown that the plasma of certain humans lacks albumin. These subjects are said to exhibit analbuminemia. One cause of this condition is a mutation that affects spUcing. Subjects with analbuminemia show only moderate edema, despite the fact that albumin is the major determinant of plasma osmotic pressure. It is thought that the amounts of the other plasma proteins increase and compensate for the lack of albumin. 

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