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- Abou-Hachem, Maher, et al.
(författare)
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Calcium binding and thermostability of carbohydrate binding module CBM4-2 of Xyn10A from Rhodothermus marinus.
- 2002
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 41:18, s. 5720-5729
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Tidskriftsartikel (refereegranskat)abstract
- Calcium binding to carbohydrate binding module CBM4-2 of xylanase 10A (Xyn10A) from Rhodothermus marinus was explored using calorimetry, NMR, fluorescence, and absorbance spectroscopy. CBM4-2 binds two calcium ions, one with moderate affinity and one with extremely high affinity. The moderate-affinity site has an association constant of (1.3 +/- 0.3) x 10(5) M(-1) and a binding enthalpy DeltaH(a) of -9.3 +/- 0.4 kJ x mol(-1), while the high-affinity site has an association constant of approximately 10(10) M(-1) and a binding enthalpy DeltaH(a) of -40.5 +/- 0.5 kJ x mol(-1). The locations of the binding sites have been identified by NMR and structural homology, and were verified by site-directed mutagenesis. The high-affinity site consists of the side chains of E11 and D160 and backbone carbonyls of E52 and K55, while the moderate-affinity site comprises the side chain of D29 and backbone carbonyls of L21, A22, V25, and W28. The high-affinity site is in a position analogous to the calcium site in CBM4 structures and in a recent CBM22 structure. Binding of calcium increases the unfolding temperature of the protein (T(m)) by approximately 23 degrees C at pH 7.5. No correlation between binding affinity and T(m) change was noted, as each of the two calcium ions contributes almost equally to the increase in unfolding temperature.
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| 2. |
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| 3. |
- Kourmouli, Niki, et al.
(författare)
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Heterochromatin and tri-methylated lysine 20 of histone H4 in animals
- 2004
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Ingår i: Journal of Cell Science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 117:14, s. 2491-2501
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Tidskriftsartikel (refereegranskat)abstract
- Tri-methylated lysine 20 on histone H4 (Me(3)K20H4) is a marker of constitutive heterochromatin in murine interphase and metaphase cells. Heterochromatin marked by Me(3)K20H4 replicates late during S phase of the cell cycle. Serum starvation increases the number of cells that exhibit high levels of Me(3)K20H4 at constitutive heterochromatin. Me(3)K20H4 is also present at the centromeric heterochromatin of most meiotic chromosomes during spermatogenesis and at the pseudoautosomal region, as well as at some telomeres. It is not present on the XY-body. During murine embryogenesis the maternal pronucleus contains Me(3)K20H4; Me(3)K20H4 is absent from the paternal pronucleus. On Drosophila polytene chromosomes Me(3)K20H4 is present in a `punctate pattern' at many chromosomal bands, including the chromocenter. In coccids it is present on the facultatively heterochromatinised paternal chromosome set. We also present evidence that Me(3)K20H4 is dependent upon H3-specific Suv(3)9 histone methyltransferase activity, suggesting that there may be `epigenetic cross-talk' between histones H3 and H4.
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