The ATP-dependent HslVU protease from Escherichia coli is a four-ring structure resembling the proteasome.

HslVU is a new two-component protease in Escherichia coli composed of the proteasome-related peptidase HslIV and the ATPase HsIU. We have used electron microscopy and image analysis to examine the structural organization of HslV and HslU homo-oligomers and the active HslVU enzyme. Electron micrographs of HslV reveal ring-shaped particles, and averaging of top views reveal six-fold rotational symmetry, in contrast to other beta-type proteasome subunits, which form rings with seven-fold symmetry.

Structural studies on the 2.25-MDa homomultimeric phosphoenolpyruvate synthase from Staphylothermus marinus.

The phosphoenolpyruvate synthase of the hyperthermophilic archaeon Staphylothermus marinus forms an unusually large homomultimeric complex of 93 kDa subunits. Electron image analysis of negatively stained and low-dose unstained preparations showed that the complex has a single, stable characteristic view and a well-preserved core with threefold rotational symmetry. The periphery of the assembly is composed of a nebulous, possibly flexible, component.

Picrophilus gen. nov., fam. nov.: a novel aerobic, heterotrophic, thermoacidophilic genus and family comprising archaea capable of growth around pH 0.

Two species belonging to a novel genus of archaea, designated Picrophilus oshimae and Picrophilus torridus, have been isolated from two different solfataric locations in northern Japan. One habitat harboring both organisms was a dry, extremely acidic soil (pH < 0.5) that was heated by solfataric gases to about 55 degrees C.

Domain structure of the Acetogenium kivui surface layer revealed by electron crystallography and sequence analysis.

The three-dimensional structure of the Acetogenium kivui surface layer (S-layer) has been determined to a resolution of 1.7 nm by electron crystallographic techniques. Two independent reconstructions were made from layers negatively stained with uranyl acetate and Na-phosphotungstate.

Localization of a sequence motif complementary to the nuclear localization signal in proteasomes from Thermoplasma acidophilum by immunoelectron microscopy.

A sequence motif complementary to the nuclear localization signal (NLS) has been localized in proteasomes from Thermoplasma acidophilum by immunoelectron microscopy using sequence-specific antibodies. The antibodies were generated in two different ways: by immunization with a carrier-coupled peptide and by isolation of the sequence-specific antibody from an immune serum against native proteasomes using a peptide-affinity column. The sequence specificity of the isolated antibody was confirmed by a PEPSCAN-ELISA performed on overlapping nonapeptides deduced from the sequence of the alpha-subunit of the Thermoplasma proteasome.

The three-dimensional structure of the regular surface protein of Comamonas acidovorans derived from native outer membranes and reconstituted two-dimensional crystals.

The three-dimensional structure of the regular surface protein (p4 symmetry, lattice constant a = b = 10.5 nm) of Comamonas acidovorans has been determined to a resolution of about 1.5 nm by means of electron microscopy and image processing.

Three-dimensional structure of the surface protein layer (MW layer) of Bacillus brevis 47.

The three-dimensional (3D) structure of one surface protein layer from Bacillus brevis 47, the middle wall (MW) layer, has been reconstructed from tilted-view electron micrographs after correlation averaging to a resolution of 2 nm. The MW layer has p6 symmetry with a center-to-center spacing of 18.3 nm and a minimum thickness of 5.

Three-dimensional structure of the surface protein of Desulfurococcus mobilis.

The spherical cells of the thermophilic, sulfur-dependent archaebacterium Desulfurococcus mobilis are completely covered with a relatively poorly ordered, tetragonally arrayed surface protein. The structure of this surface protein was examined by using three-dimensional electron microscopy. The protein lattice forms an open meshwork composed of cross-shaped morphological units, which are released when glycerol is added.