1. |
|
|
2. |
|
|
3. |
|
|
4. |
|
|
5. |
|
|
6. |
- Griffiths, G, et al.
(författare)
-
Characterization of the glycosyltransferase enzyme from the Escherichia coli K5 capsule gene cluster and identification and characterization of the glucuronyl active site.
- 1998
-
Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 273:19, s. 11752-7
-
Tidskriftsartikel (refereegranskat)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.
|
|
7. |
- Møller, Ian M., et al.
(författare)
-
Ubiquinone-1 induces external deamino-NADH oxidation in potato tuber mitochondria
- 1996
-
Ingår i: Plant Physiology. - 0032-0889. ; 112:1, s. 75-78
-
Tidskriftsartikel (refereegranskat)abstract
- The addition of ubiquinone-1 (UQ-1) induced Ca2+-independent oxidation of deamino-NADH and NADH by intact potato (Solanum tuberosum L. cv Bintje) tuber mitochondria. The induced oxidation was coupled to the generation of a membrane potential. Measurements of NAD+-malate dehydrogenase activity indicated that the permeability of the inner mitochondrial membrane to NADH and deamino-NADH was not altered by the addition of UQ-1. We conclude that UQ-1-induced external deamino-NADH oxidation is due to a change in specificity of the external rotenone-insensitive NADH dehydrogenase. The addition of UQ-1 also induced rotenone-insensitive oxidation of deamino-NADH by inside-out submitochondrial particles, but whether this was due to a change in the specificity of the internal rotenone-insensitive NAD(P)H dehydrogenase or to a bypass in complex I could not be determined.
|
|
8. |
|
|
9. |
|
|
10. |
|
|