Molecular cloning of rat intestinal mucin. Lack of conservation between mammalian species

We have prepared antisera to deglycosylated rat intestinal mucin and used it to obtain immunoreactive clones from a rat jejunum cDNA library. Four of these clones were sequenced, and all were found to be partial cDNAs that contained 18-base pair tandem repeats characteristic of a mucin. These cDNAs encoded a repetitive peptide with a consensus sequence of TTTPDV. Thus, they bear little resemblance to either of the two human intestinal mucin cDNAs isolated previously (Gum, J. R., Byrd, J. C., Hicks, J. W., Toribara, N. W., Lamport, D. T. A., and Kim, Y. S. (1989) J. Biol. Chem. 264, 6480-6487 and Gum, J. R., Hicks, J. W., Swallow, D. M., Lagace, R. E., Byrd, J. C., Lamport, D. T. A., Siddiki, B., and Kim, Y. S. (1990) Biochem. Biophys. Res. Commun. 171, 407-415). One of these rat mucin clones, designated RMUC 176, was chosen for further analysis. This clone recognized a band of approximately 9 kilobases when used to probe RNA blots. A strong hybridization band was present using rat small intestine and colon RNA but was not detectable when RNA isolated from heart, liver, or kidney was tested. The RMUC 176 clone and the two previously isolated human intestinal mucin cDNA clones were used to probe blots prepared from BamHI-digested DNA of various species. Here, the human probes detected fragments present only in human and chimpanzee DNA, whereas the RMUC 176 clone recognized fragments only in rat and mouse DNA. Thus, the repetitive portions of intestinal mucin genes are apparently not well conserved between phylogenetically distant species.     

Molecular cloning of cDNAs derived from a novel human intestinal mucin gene

A human small intestinal lambda gt11 cDNA library was screened with antibodies to deglycosylated small intestinal mucin. Four partial cDNA clones were isolated that define a novel human mucin gene. These include two partial cDNA clones, SIB 124 and SIB 139, that contain 51 nucleotide tandem repeats which encode a seventeen amino acid repetitive peptide with a consensus sequence of HSTPSFTSSITTTETTS. SIB 139 hybridized to messages produced by small intestine, colon, colonic tumors and also by high mucin variant LS174T colon cancer cells. The gene from which cDNAs SIB 124 and SIB 139 are derived (proposed name MUC 3) maps to chromosome 7, distinct from other known human mucin genes.     

Monitoring of environmental arsenic by cultures of the photosynthetic bacterial sensor illuminated with a near-infrared light emitting diode array

Recombinant Rhodopseudomonas palustris, harboring the carotenoid-metabolizing gene crtI (CrtIBS), and whose color changes from greenish yellow to red in response to inorganic As(III), was cultured in transparent microplate wells illuminated with a light emitting diode (LED) array. The cells were seen to grow better under near-infrared light, when compared with cells illuminated with blue or green LEDs. The absorbance ratio of 525 to 425 nm after cultivation for 24 h, which reflects red carotenoid accumulation, increased with an increase in As(III) concentrations. The detection limit of cultures illuminated with near-infrared LED was 5 microgram/l, which was equivalent to that of cultures in test tubes illuminated with an incandescent lamp. A near-infrared LED array, in combination with a microplate, enabled the simultaneous handling of multiple cultures, including CrtIBS and a control strain, for normalization by the illumination of those with equal photon flux densities. Thus, the introduction of a near-infrared LED array to the assay is advantageous for the monitoring of arsenic in natural water samples that may contain a number of unknown factors and, therefore, need normalization of the reporter event.     

Alterations of O-glycan biosynthesis in human colon cancer tissues

Human colon cancer is associated with antigenic and structuralchanges in mucin-type carbohydrate chains (O-glycans). To elucidatethe control of the biosynthesis of these O-glycans in coloncancer, we have studied glycosyltransferase and sulphotransferaseactivities involved in the assembly of elongated O-glycan structures.We analysed homogenates prepared from cancer tissue, adjacentnormal and distal normal tissue from 20 patients. Several transferaseactivities showed pronounced changes in cancer tissue. The changescorrelate with previous findings of a loss of O-glycans in cancermucins, but did not always correlate with levels of Tn, sialyl-Tn,T and Le^x antigens in homogenates or with the differentiationstatus and Duke's stages of the cancer tissue or the patient'sblood type, sex and age. UDP-GlcNAc: Gal NAc-R ß3-N-acetylglucosaminyltransferase(where GlcNAc is N-acetyl-D-glucosamine and GalNAc is N-acetyl-D-galactosamine)synthesizing O-glycan core 3, GlcNAcß1-3GalNAc-, CMP-sialicacid: GalNAc-peptide