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L M Amzel

Publications and source records attributed to L M Amzel.

At least 91 records · Page 5Linked to original sources
PubMed1981

Structure of F1-ATPase.

F1-ATPases are large multimeric proteins that can be isolated from the membrane bound system that catalyzes the phosphorylation of ADP by inorganic phosphate in bacteria, plants, and mitochondria. They can be visualized in electron micrographs of the inner mitochondrial membranes where they appear as large protruding spheres 90 A in diameter. The purified F1-ATPases have a molecular weight of 320,000 to 400,000 daltons and are composed of five non-identical subunits (alpha, beta, gamma, delta and epsilon). The stoichiometry of these subunits in the complex is still unknown but compositions of the type alpha3beta3gamma delta epsilon and alpha2beta2gamma2delta2epsilon2 were found to be consistent with some of the available experimental data. This review discusses the recent data and the experimental approaches utilized for the structural characterization of F1-ATPases.

Adenosine Triphosphatases↗
PubMed1978

Adenosine triphosphatase from rat liver mitochondria. Crystallization and x-ray diffraction studies of the F1-component of the enzyme.

The homogeneous rat liver F1-ATPase preparation of Catterall and Pedersen (Catterall, W.A., and Pedersen, P.L. (1971) J. Biol. Chem. 246, 4987-4994) has been crystallized from a solution containing phosphate and ATP by precipitation with ammonium sulfate. Most of the resultant crystals are cubes of approximately 0.3 to 0.6 mm per side. X-ray precession photographs show that the crystals are rhombohedral, space group R32 (D37 NO155) with hexagonal cell dimensions a = 148 A, c = 368 A. The molecular weight of the asymmetric unit of the crystals is 190,000 or about half the molecular weight (384,000) of the rat liver enzyme indicating that the crystallographic 2-fold axes of symmetry coincide with a molecular symmetry axis. The crystals diffract to at least 3.5 A and therefore this is the first report of an ATPase preparation in which crystals suitable for x-ray analysis have been obtained.

Adenosine Triphosphatases↗
PubMed1975

Structure and specificity of antibody molecules.

The structure of the Fab' fragment of a human myeloma protein (IgG1 (lambda) New) has been determined by X-ray crystallographic analysis to a nominal resolution of 0.2 nm. Each of the structure subunits corresponding to the variable and to the constant homology regions of the light and heavy polypeptide chains contains two irregular beta-sheets which are roughly parallel to each other and surround a tighly packed interior of hydrophobic side chains. The regions of the hypervariable sequences in the light and heavy chains occur in close spatial proximity at one end of the molecule, defining the active site of IgG New. The role of these hypervariable regions in defining the size and shape of the active site of different immunoglobulins is discussed on the basis of the three-dimensional model of Fab' New. Several ligands that bind to the active centre of IgG New have been used to obtain crystalline ligand-Fab' New complexes which were investigated by difference Fourier maps. These studies are analysed in terms of the biological function and specificity of antibodies.

Amino Acid Sequence↗
PubMed1974

The three dimensional structure of a combining region-ligand complex of immunoglobulin NEW at 3.5-A resolution.

IgG New binds ligands such as orceine, menadione, and uridine with a low affinity (K(0) about 1 x 10(3) liter/mol) and a gamma-hydroxy derivative of vitamin K(1) with a higher affinity (K(0) = 1.7 x 10(5) liter/mol). Binding studies indicate that both the 2-methylnaphthoquinone rings and the phytyl tail of the vitamin K(1) hapten contribute to the total binding energy. The binding of these ligands in the crystalline state has been investigated by difference Fourier maps of Fab' New-ligand complexes at 6-A resolution. A 3.5-A resolution difference Fourier map obtained for the gamma-hydroxy derivative of the vitamin K(1)-Fab' complex shows that this hapten is bound in a shallow groove or crevice between the light and the heavy chains, in close proximity to the polypeptide segments containing the hypervariable regions. At least 12 amino-acid residues from both the light and the heavy chains appear to be in close contact with the ligand. No major conformational changes were detected in the Fab' fragment after ligand binding.

Antigen-Antibody Complex↗
PubMed1974

The three-dimensional structure of the fab' fragment of a human myeloma immunoglobulin at 2.0-angstrom resolution.

The structural analysis of the Fab' fragment of human myeloma immunoglobulin IgGl(lambda) New has been extended to a nominal resolution of 2.0 A. Each of the structural subunits corresponding to the variable and to the constant homology regions of the light and heavy chains contains two irregular beta-sheets which are roughly parallel to each other and surround a tightly packed interior of hydrophobic side chains. About 50-60% of the amino-acid residues are included in beta-pleated sheets. Sequence alignments between the homology regions of Fab' New obtained by comparison of their three-dimensional structures are given. Some of the sequence variations observed in light and heavy chains and the role of the regions of hypervariable sequence in defining the size and shape of the active site of different immunoglobulin molecules are discussed on the basis of the three-dimensional model of Fab' New.

Amino Acid Sequence↗
PubMed1973

Three-dimensional structure of the Fab' fragment of a human immunoglobulin at 2,8-A resolution.

The structure of the Fab' fragment of a human myeloma immunoglobulin was determined by x-ray crystallographic analysis at 2.8-A resolution. The Fourier map of the electron density was correlated with the aminoacid sequence to obtain a three-dimensional model. Four globular subunits, which correspond to the homology regions of the light and heavy chains, are arranged in a tetrahedral configuration. These subunits closely resemble each other, sharing a basic pattern of polypeptide chain folding. In each subunit, long sequences of tightly packed, hydrogen bonded polypeptide chain run parallel to the major axis of the subunit. No helical conformation can be seen. Different patterns of interchain disulfide linkage and unusual intrachain disulfide bonds that have been observed in other immunoglobulins can be explained with this model. The regions of hypervariable sequences in the light and heavy chains occur at one end of the molecule, in close spatial proximity.

Amino Acid Sequence↗