1. |
|
|
2. |
|
|
3. |
- Griffiths, G, et al.
(author)
-
Characterization of the glycosyltransferase enzyme from the Escherichia coli K5 capsule gene cluster and identification and characterization of the glucuronyl active site.
- 1998
-
In: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 273:19, s. 11752-7
-
Journal article (peer-reviewed)abstract
- Bacterial capsular polysaccharides play an important role in virulence and survival. The Escherichia coli K5 capsule consists of a repeat structure of -4)GlcA-beta(1,4)-GlcNAc alpha(1-, identical to N-acetylheparosan. A 60-kDa protein, KfiC, has been identified as a bifunctional glycosyltransferase, responsible for the alternating alpha and beta addition of each UDP-sugar to the nonreducing end of the polysaccharide chain. Using hydrophobic cluster analysis, a conserved secondary structure motif characteristic of beta-glycosyltransferases was identified along with two highly conserved aspartic acid residues at positions 301 and 352 within the KfiC protein. Site-directed mutagenesis was used to identify catalytically active amino acids within domain A of the KfiC protein. The conserved aspartic acid residues at 301 and 352 were shown to be critical for the beta addition of UDP-GlcA (uridine diphosphoglucuronic acid) to defined nonreducing end oligosaccharide acceptors, suggesting that these conserved aspartic acid residues are catalytically important for beta-glycosyltransferase activity. A deleted derivative of the kfiC gene was generated, which encoded for a truncated KfiC (kfiC') protein. This protein lacked 139 amino acids at the C terminus. This enzyme had no UDP-GlcA transferase activity but still retained UDP-GlcNAc transferase activity, indicating that two separate active sites are present within the KfiC protein.
|
|
4. |
|
|
5. |
- Van, den Berg M, et al.
(author)
-
Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife
- 1998
-
In: ENVIRONMENTAL HEALTH PERSPECTIVES. - : US DEPT HEALTH HUMAN SERVICES PUBLIC HEALTH SERVICE. ; 106:12, s. 775-792
-
Review (other academic/artistic)abstract
- An expert meeting was organized by the World Health Organization (WHO) and held in Stockholm on 15-18 June 1997. The objective of this meeting was to derive consensus toxic equivalency factors (TEFs) for polychlorinated dibenzo-p-dioxins (PCDDs) and diben
|
|
6. |
|
|
7. |
|
|
8. |
|
|