UL25 and UL17 are two essential minor capsid proteins of HSV-1, implicated in DNA packaging and capsid maturation. We used cryo-electron microscopy to examine their binding to capsids, whose architecture observes T = 16 icosahedral geometry. C-capsids (mature DNA-filled capsids) have an elongated two-domain molecule present at a unique, vertex-adjacent site that is not seen at other quasiequivalent sites or on unfilled capsids. Using SDS-PAGE and mass spectrometry to analyze wild-type capsids, UL25 null capsids, and denaturant-extracted capsids, we conclude that (1) the C-capsid-specific component is a heterodimer of UL25 and UL17, and (2) capsids have additional populations of UL25 and UL17 that are invisible in reconstructions because of sparsity and/or disorder. We infer that binding of the ordered population reflects structural changes induced on the outer surface as pressure builds up inside the capsid during DNA packaging. Its binding may signal that the C-capsid is ready to exit the nucleus.

Transglutaminase activity was found to be present in highly purified non-synaptosomal rat brain mitochondria. A 78-kDa protein in these organelles was shown to be a transglutaminase 2 substrate, and incubation of a non-synaptosomal mitochondrial lysate with transglutaminase 2 yielded high-Mr proteins. The 78-kDa protein was identified as mitochondrial aconitase by MALDI-TOF analysis. Aconitase activity was decreased in a dose-dependent manner when non-synaptosomal rat brain mitochondria were incubated with transglutaminase 2. Transglutaminase activity is increased about 2-fold in the mitochondrial fraction of HD caudate. Moreover, Western blotting of the mitochondrial fraction revealed that most of the mitochondrial aconitase in HD caudate is present as high-Mr aggregates. Aconitase activity was previously shown to be decreased in Huntington disease (HD) caudate (a region severely damaged by the disease). The present findings suggest that an increase of transglutaminase activity in HD caudate may contribute to mitochondrial dysfunction by incorporating aconitase into inactive polymers.

Monomeric human calcitonin (hCT) gene and oligomeric hCT genes composed of two, three or four head-to-tail linked monomers were fused in-frame to the yeast alpha-factor leader coding sequence wild-type and fragile mutant Saccharomyces cerevisiae strains were transformed with the constructed plasmids and the yield of recombinant protein secreted into the culture medium was measured. The yeast cells secreted equal (molar) amounts of all of the hCT variants. The recombinant proteins remained stable in the growth medium for at least 3 days. The fragile cells secreted about 30% more hCT as compared to the wild-type yeast cells.

The primary structure of 20β‐hydroxysteroid dehydrogenase from Streptomyces hydrogenans was determined after FPLC purification of a commercial preparation. Peptides obtained from different proteolytic cleavages were purified by reverse phase HPLC. The 255‐residue structure deduced was found to be distantly homologous to those of Drosophila alcohol dehydrogenase and several other dehydrogenases, establishing that prokaryotic 20β‐hydroxysteroid dehydrogenase as a member of the ‘short‐chain alcohol dehydrogenase family’. With the enzymes characterized, the identity is greatest (31–34%) towards 4 other prokaryotic dehydrogenases, but the family also includes mammalian steroid and prostaglandin dehydrogenases. These enzymes are low in Cys and have a strictly conserved Tyr residue that appears to be important.