Exclusive CO binding to cytochrome oxidase

CO added to dithionite-reduced cytochrome oxidase pretreated with azide, cyanide, or fluoride yielded CO-ferrous heme a3 trapping the unliganded reduced heme. Ferrous heme a3 was either an equilibrium species initially present, or provided by dissociation of ligand-bound ferric heme a3 followed by the reduction with dithionite. In the latter case the ligand dissociation was rate-limiting for the CO compound formation. Pretreatment of the enzyme with the inhibitory ligands affected neither photodissociation and reassociation of the CO compound thus formed, nor reaction with dioxygen initiated by the flow-flash method to any significant degree. Only the cyanide treatment slightly decreased the rate of intramolecular electron transfer. These results indicate that no inhibitory ligand but CO remains in the vicinity of the heme a3-CuB center in the CO compound of cytochrome oxidase.     

Role of DNA aneuploidy, overexpression of p53 gene product, and cellular proliferation in the progression of gastric cancer.

DNA aneuploidy, p53 overexpression, and high cell proliferation frequently occur in gastric cancer. However, little is known about the time of their appearance throughout cancer progression. Therefore, the objective of the present study was to determine when such abnormalities occur during gastric cancer progression. We classified the gastric cancers examined into intestinal (n = 65) and diffuse (n = 34) types. DNA ploidy was examined using flow cytometry and expression of MIB-1 and p53 immunoreactivity were studied using the avidin-biotin complex method in three stages of gastric cancer (mucosal, submucosal, deeply invasive cancer, i.e., advanced cancer). The incidence of DNA aneuploidy in intestinal-type mucosal cancers (15/27, 55.6%) was lower than that of submucosal invasive cancers (14/16, 87.5%) or advanced cancers (19/22, 86.4%), while a low incidence of DNA aneuploidy was observed in each diffuse-type cancer group (mucosal, 1/12, 8.3%; submucosal invasive, 3/9, 33.3%; advanced, 8/14, 57.1%). Although overexpression of the p53 gene in intestinal-type cancer was found in early stage, that in diffuse-type cancer was observed in advanced stage. Among the intestinal-type mucosal cancers, the MIB-1 percent positive was higher in aneuploid tumors than diploid ones. DNA aneuploidy and overexpression of the p53 gene may play an important role in the early tumorigenesis of intestinal-type gastric cancer and in the late event of tumorigenesis of diffuse-type gastric cancer.     

Resonance Raman spectra of heme a derivatives. Evidence for the reaction of peripheral formyl group with HCN and NaHSO3.

A separate and distinct population of polyribosomes exists in the detergent-washed nuclei of adenovirus-infected HeLa cells. These polyribosomes, released by exposure to polynucleotides such as high molecular weight nuclear RNA or poly(U), do not appear to be cytoplasmic contaminants. Nuclear polyribosomes have a considerably lower buoyant density compared to cytoplasmic ones. Nuclear polyribosomes, in a cell-free system of protein synthesis, are six- to eight-fold less active compared to cytoplasmic ones and are insensitive to aurin tricarboxylic acid. They do not complement cytoplasmic polyribosomes in protein synthesis in the cell-free system. Finally, the number of proteins synthesized by nuclear polyribosomes is higher compared with that synthesized by the cytoplasmic ones. Only the virus-specific proteins, including P-VII, are synthesized by cytoplasmic polyribosomes. Nuclear polyribosomes, on the other hand, synthesize virusspecific proteins, including P-VII and VII, and a number of additional proteins not synthesized by the cytoplasmic ones.