0000000000210382
AUTHOR
J. R. Harris
Structure of a molluscan hemocyanin didecamer (HtH1 from Haliotis tuberculata) at 12 Å resolution by cryoelectron microscopy
A 12 A resolution three-dimensional density map of the Haliotis tuberculata hemocyanin type 1 (HtH1) didecamer has been obtained by cryoelectron microscopy of unstained molecules and angular reconstitution. The dyad symmetry of the 8 MDa D5 HtH1 didecamer, formed by the pairing of two asymmetric 4 MDa ring-like C5 decamers, is emphasised. The major and minor surface helical grooves of the didecamer are well defined, in agreement with earlier data on molluscan hemocyanins. The location of the obliquely orientated repeating unit, a subunit dimer, within the decamer has been defined. Following interactive extraction of this dimer, several new structural features of the dimer and of the subunit…
Electron microscopy of a double helical tubular filament in keyhole limpet (Megathura crenulata) hemolymph.
A approximately 25 nm hollow double helical filament has been detected ultrastructurally in the cell-free supernatant from hemolymph of the keyhole limpet Megathura crenulata (Gastropoda: Prosobranchia: Fissurellidae). Subsequently, much higher concentrations of this material were found in the cell pellet from hemolymph. Both negative staining and thin sectioning have been performed in an attempt to obtain a preliminary structural characterization of this new filament. It is proposed that the filaments are released or secreted from blood hemocytes in response to bleeding, but it has not been possible to define absolutely an intracellular organelle containing this material. It is shown that …
Amylopectin: a major component of the residual body inCryptosporidium parvumoocysts
Amylopectin is used for carbohydrate storage in different life-stages of a number of apicomplexan parasites. We have performed an ultrastructural analysis of amylopectin granules from the oocyst residual body and sporozoites ofCryptosporidium parvum. Amylopectin granules were studiedin situand after isolation from ‘French’ press disrupted parasites, by conventional transmission electron microscopy (TEM) of sectioned oocysts and various negative staining and cryoelectron microscopy techniques. Within the membrane-enclosed oocyst residuum large amylopectin granules (0·1–0·3 μm) can be found besides a characteristic large lipid body and a crystalline protein inclusion. Smaller granules were de…
Electron Microscopy of Human Erythrocyte Catalase: New Two-Dimensional Crystal Forms
Abstract Using the mica-spreading "negative staining-carbon film" procedure, human erythrocyte catalase has been shown to create a number of different periodic or crystalline two-dimensional (2-D) arrays which differ in the arrangement of molecules in the repeating units and the lattice type. Digital image processing has been performed with a 2-D array which contains regularly arranged "undulating" rows of molecules and also with a 2-D crystal form, exhibiting pgg (p22 1 2 1 ) symmetry and lattice parameters of a = 12.7 nm, b = 44 nm, and γ= 92°. The data are compared with our previous analysis of a different human erythrocyte catalase 2-D crystal, and the effect of partial-depth negative s…
Transmission Electron Microscopy of GroEL, GroES, and the Symmetrical GroEL/ES Complex
Two new 2-D crystal forms of the Escherichia coli chaperone GroEL (cpn60) 2 x 7-mer have been produced using the negative staining-carbon film (NS-CF) technique. These 2-D crystals, which contain the cylindrical GroEL in side-on and end-on orientations, both possess p21 symmetry, with two molecules in the respective unit cells. The crystallographically averaged images correlate well with those obtained by other authors from single particle analysis of GroEL and our own previous crystallographic analysis. 2-D crystallization of the smaller chaperone GroES (cpn10) 7-mer has also been achieved using the NS-CF technique. Crystallographically averaged images of GroES single particle images indic…