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E Subramanian

Publications and source records attributed to E Subramanian.

31 records · Page 2Linked to original sources
PubMed1984

Structure and conformation of linear peptides. III. Structure of glycyl-glycyl-L-valine.

The tripeptide, glycyl-glycyl-L-valine, crystallizes as a dihydrate in the monoclinic space group P2(1), with a = 5.786(1), b = 7.954(2), c = 14.420(3)A, beta = 93.85(2) degrees, Z = 2. The structure was solved by direct methods and refined to an R-value of 0.040 for 876 observed reflections. The molecule exists as a zwitterion in the crystal. The peptide planes show significant deviations from planarity. The chain conformation resembles a reverse turn if the orientation of the carboxyl group is also taken into account. An intramolecular water bridge links the amino and carboxyl ends of the molecule. The crystal packing involves spatial segregation of polar and nonpolar moieties.

Crystallography↗
PubMed1982

Three-dimensional structure of the complex of the Rhizopus chinensis carboxyl proteinase and pepstatin at 2.5-A resolution.

An X-ray diffraction analysis has been carried out at 2.5-A resolution of the three-dimensional structure of the Rhizopus chinensis carboxyl proteinase complexed with pepstatin. The resulting model of the complex supports the hypothesis [Marciniszyn, J., Hartsuck, J.A., & Tang, J. (1976) J. Biol. Chem. 251, 7088-7094] that statine (3-hydroxy-4-amino-6-methylheptanoic acid) approaches an analogue of the transition state for catalysis. The way in which pepstatin binds to the enzyme can be extended to provide a model of substrate binding and a model of the transition-state complex. This in turn has led to a proposed mechanism of action based on general acid-base catalysis with no covalent intermediates. These predictions are in general agreement with kinetic studies using several carboxyl proteinases, which together with their sequence homology and their common three-dimensional structures suggest that this mechanism can be extrapolated to all carboxyl proteinases.

Aspartic Acid Endopeptidases↗
PubMed1977

The crystal structure of an acid protease from Rhizopus chinensis at 2.5 A resolution.

This paper contains a preliminary report of the crystal structure of the acid protease from Rhizopus chinensis at 2.5 A resolution. The molecule is bilobal with a large cleft between the lobes. Pepstatin binds in the cleft near the catalytically active Asp-35. The overall folding of the molecule consists primarily of antiparallel beta-strands, there being only four small helices.

Binding Sites↗
PubMed1977

Homology among acid proteases: comparison of crystal structures at 3A resolution of acid proteases from Rhizopus chinensis and Endothia parasitica.

The molecular structures of two fungal acid proteases at 3 A resolution have been compared, and found to have similar secondary and tertiary folding. These enzymes are bilobal and have a pronounced cleft between the two lobes. This cleft has been identified as the active site region from inhibitor binding studies. The results of the comparison are discussed in terms of homology among the acid proteases in general.

Ascomycota↗
PubMed1976

Interactions of hydrated metal ions with nucleotides: the crystal structure of barium adenosine 5'-monophosphate heptahydrate.

The crystal and molecular structure of barium adenosine 5'-monophosphate heptahydrate was determined from x-ray diffraction data. Crystals of barium adenosine 5'-monophosphate heptahydrate are monoclinic, space group C2, with a = 32.559(3), b = 6.969(3), c = 9.597(1) A, and beta = 100.31(1) degrees. Intensity data were collected with an automated diffractometer. The structure was solved by the heavy-atom method and refined by least-squares to R = 0.034. This structure provides an example of an outer-sphere metal-nucleotide complex, in which a completely hydrated metal ion interacts with the nucleotide only through water bridges. The barium ion is coordinated to eight water molecules, which form a slightly distorted square antiprism. Seven of the eight water molecules from the barium hydration shell are hydrogen bonded to phosphate groups; three of these water molecules are also hydrogen bonded to other suitable acceptor sites on the base and ribose moieties. The conformation about the glycosidic bond is anti, with chiCN = 69 degrees, and, as in most nucleotide structures, the conformation about the C(4')-C(5') bond is gauche-gauche. However, the ribose displays an unusual conformation (best described as C(4')-exo) not previously observed in crystal structures of nucleosides or nucleotides, other than 3',5'-cyclic nucleotides. It is possible that this unusual conformation is a consequence of the metal-water-nucleotide bridging interactions.

Adenosine Monophosphate↗