Biomaterial Database

Direct observation of better hydration at the N terminus of an alpha-helix with glycine rather than alanine as the N-cap residue. 1994

Y Harpaz, and N Elmasry, and A R Fersht, and K Henrick

Centre for Protein Engineering, Medical Research Council Centre, Cambridge, United Kingdom.

The structural basis for the stability of N termini of helices has been analyzed by thermodynamic and crystallographic studies of three suitably engineered mutants of the barley chymotrypsin inhibitor 2 with Ser, Gly, or Ala at the N-cap position (residue 31). Each mutant has a well-organized shell of hydration of the terminal NH groups of the helix. The three structures are virtually superimposable (rms separations for all atoms, including the common water molecules, are 0.15-0.17 A) and show neither changes in conformation at the site of substitution nor changes in the crystal packing. The only changes on going from Ser-31 to Ala-31 to Gly-31 are in the position of a water molecule (Wat-116). This is bound to the Ser-O gamma atom in the Ser-31 structure but is in a weak hydrogen bonding position with the NH of residue 34 (O ... N = 3.28 A) in the Ala-31 mutant, partly replacing the strong Ser-31-O gamma ... N34 hydrogen bond (O ... N = 2.65 A). The corresponding water molecule completely replaces the Ser hydroxyl hydrogen bond to N34 on mutation to Gly (2.74 A). The only other change between the three structures is an additional water molecule in the Ala-31 structure (Wat-150) that partly compensates for the weak Wat-116 ... N34 hydrogen bond. Perturbation of solvation by the side chain of Ala is consistent with earlier hypotheses on the importance of exposure of the termini of helices to the aqueous solvent.

UI	MeSH Term	Description	Entries
D008958	Models, Molecular	Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.	Molecular Models,Model, Molecular,Molecular Model
D010455	Peptides	Members of the class of compounds composed of AMINO ACIDS joined together by peptide bonds between adjacent amino acids into linear, branched or cyclical structures. OLIGOPEPTIDES are composed of approximately 2-12 amino acids. Polypeptides are composed of approximately 13 or more amino acids. PROTEINS are considered to be larger versions of peptides that can form into complex structures such as ENZYMES and RECEPTORS.	Peptide,Polypeptide,Polypeptides
D010940	Plant Proteins	Proteins found in plants (flowers, herbs, shrubs, trees, etc.). The concept does not include proteins found in vegetables for which PLANT PROTEINS, DIETARY is available.	Plant Protein,Protein, Plant,Proteins, Plant
D011506	Proteins	Linear POLYPEPTIDES that are synthesized on RIBOSOMES and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of AMINO ACIDS determines the shape the polypeptide will take, during PROTEIN FOLDING, and the function of the protein.	Gene Products, Protein,Gene Proteins,Protein,Protein Gene Products,Proteins, Gene
D011994	Recombinant Proteins	Proteins prepared by recombinant DNA technology.	Biosynthetic Protein,Biosynthetic Proteins,DNA Recombinant Proteins,Recombinant Protein,Proteins, Biosynthetic,Proteins, Recombinant DNA,DNA Proteins, Recombinant,Protein, Biosynthetic,Protein, Recombinant,Proteins, DNA Recombinant,Proteins, Recombinant,Recombinant DNA Proteins,Recombinant Proteins, DNA
D002918	Chymotrypsin	A serine endopeptidase secreted by the pancreas as its zymogen, CHYMOTRYPSINOGEN and carried in the pancreatic juice to the duodenum where it is activated by TRYPSIN. It selectively cleaves aromatic amino acids on the carboxyl side.	Alpha-Chymotrypsin Choay,Alphacutanée,Avazyme
D005998	Glycine	A non-essential amino acid. It is found primarily in gelatin and silk fibroin and used therapeutically as a nutrient. It is also a fast inhibitory neurotransmitter.	Aminoacetic Acid,Glycine, Monopotassium Salt,Glycine Carbonate (1:1), Monosodium Salt,Glycine Carbonate (2:1), Monolithium Salt,Glycine Carbonate (2:1), Monopotassium Salt,Glycine Carbonate (2:1), Monosodium Salt,Glycine Hydrochloride,Glycine Hydrochloride (2:1),Glycine Phosphate,Glycine Phosphate (1:1),Glycine Sulfate (3:1),Glycine, Calcium Salt,Glycine, Calcium Salt (2:1),Glycine, Cobalt Salt,Glycine, Copper Salt,Glycine, Monoammonium Salt,Glycine, Monosodium Salt,Glycine, Sodium Hydrogen Carbonate,Acid, Aminoacetic,Calcium Salt Glycine,Cobalt Salt Glycine,Copper Salt Glycine,Hydrochloride, Glycine,Monoammonium Salt Glycine,Monopotassium Salt Glycine,Monosodium Salt Glycine,Phosphate, Glycine,Salt Glycine, Monoammonium,Salt Glycine, Monopotassium,Salt Glycine, Monosodium
D006860	Hydrogen Bonding	A low-energy attractive force between hydrogen and another element. It plays a major role in determining the properties of water, proteins, and other compounds.	Hydrogen Bonds,Bond, Hydrogen,Hydrogen Bond
D000409	Alanine	A non-essential amino acid that occurs in high levels in its free state in plasma. It is produced from pyruvate by transamination. It is involved in sugar and acid metabolism, increases IMMUNITY, and provides energy for muscle tissue, BRAIN, and the CENTRAL NERVOUS SYSTEM.	Abufène,Alanine, L-Isomer,L-Alanine,Alanine, L Isomer,L Alanine,L-Isomer Alanine
D001467	Hordeum	A plant genus of the family POACEAE. The EDIBLE GRAIN, barley, is widely used as food.	Barley,Hordeum vulgare