Biomedical subjects

G Wagner

Publications and source records attributed to G Wagner.

At least 19 recordsLinked to original sources

PubMed1997

Subunit specificity and organ distribution of glutathione transferase-catalysed S-nitrosoglutathione formation from alkyl nitrites in the rat.

Glutathione transferase (GST)-catalysed S-nitrosoglutathione (GSNO) formation from alkyl nitrites was determined with the homodimers 1-1, 2-2, 3-3, and 4-4 isolated from rat liver. The 4-4 isoform showed a high specificity for the alkyl nitrites. Total GST activities were studied in homogenates from different organs. The liver showed highest GST activity both with amyl nitrite and with 1-chloro-2,4-dinitrobenzene (CDNB) as substrate, the activity ratio of amyl nitrite over CDNB being 3.8. In lung and heart, these ratios were 6.2 and 5.7, respectively, indicating a selectivity of these organs for alkyl nitrite metabolism and GSNO formation.

Amyl Nitrite↗

PubMed1996

Backbone dynamics, amide hydrogen exchange, and resonance assignments of the DNA methylphosphotriester repair domain of Escherichia coli Ada using NMR.

The 10kDa amino-terminal fragment of Escherichia coli Ada protein (N-Ada10) repairs methyl phosphotriesters in DNA and possesses a tightly bound zinc ion. The complete resonance assignments of this protein domain have been obtained using multidimensional homonuclear and heteronuclear NMR experiments. The assignments served to study the internal mobility of this protein domain via 15N relaxation experiments. This involved the measurement of longitudinal and transverse 15N relaxation rates, as well as the amide proton solvent exchange rates. Relaxation rates in the rotating frame, R1 rho, of 15N nuclei were measured at different spin-lock field strengths, leading to the detection of two slow conformational exchange processes at Gly-25 and Gln-73. For the latter, which is next to the active site of this protein domain, the characteristic time of this process was found to be around 60 microseconds. The other relaxation experiments unveiled some regions of fast internal motions, faster than the overall correlation time. These motions were found in the N- and C- terminal tails, in segment 33-35 which forms the turn between beta-strands S1 and S2, and residues 47-52 located in a long loop preceding strand S3. The latter loop belongs to the potential DNA binding surface of N-Ada10. While the structure from residue 18 to residue 26 appears not well defined in the calculated structure, the relaxation experiments do not indicate higher mobility for this region. Residues at the N-terminal portion, including the first helix, the sequentially adjacent loop, and part of the second helix, exhibit internal motions close to the time scale of the overall rotational correlation time. This appears to be related to the fact that the first helix has no hydrogen bonds or salt bridges to the rest of the protein and is stabilized only by the involvement of some of its side chains in a hydrophobic core consisting of the side chains of two phenylalanines, a tryptophan, a leucine, and a valine. The four cysteines which bind the zinc show motions on different time scales ranging from microseconds to picoseconds. Thus the motions in the immediate region around the bound zinc of the DNA methyl phosphotriester repair domain are of relatively small amplitude but take place over a wide time range. On the other hand, high mobility is found in the turn connecting S1 and S2 and in the loop preceding S3, regions of the potential DNA binding surface.

Bacterial Proteins↗

PubMed1996

A 39 amino acid fragment of the cell cycle regulator p21 is sufficient to bind PCNA and partially inhibit DNA replication in vivo.

The cell cycle regulator p21 interacts with and inhibits the DNA replication and repair factor proliferating cell nuclear antigen (PCNA). We have defined a 39 amino acid fragment of p21 which is sufficient to bind PCNA with high affinity (Kd 10-20 nM). This peptide can inhibit DNA replication in vitro and microinjection of a GST fusion protein containing this domain inhibited S phase in vivo. Despite its high affinity for PCNA, the free 39 amino acid peptide does not have a well-defined structure, as judged from circular dichroism and nuclear magnetic resonance measurements, suggesting an induced fit mechanism for the PCNA-p21 interaction. The association of the small peptide with PCNA was thermolabile, suggesting that portions of p21 adjoining the minimal region of contact stabilize the interaction. In addition, a domain containing 67 amino acids from the N-terminus of PCNA was defined as both necessary and sufficient for binding to p21.

Amino Acid Sequence↗

PubMed1996

Internal mobility in the partially folded DNA binding and dimerization domains of GAL4: NMR analysis of the N-H spectral density functions.

The DNA binding domain (residues 1--65) of the yeast transcriptional activator GAL4 is only partially folded. While residues 10-41, the DNA recognition domain, form a well-defined structure in the free protein, the whole polypeptide folds up and dimerizes upon binding DNA. In order to describe the mobility of the protein, we have characterized the frequency spectrum of the motions of N-H bond vectors of GAL4(1-65) using a reduced spectral density mapping approach (an approximation of the full spectral density mapping technique) [Peng, J. W., & Wagner, G. (1992a) J. Magn. Reson. 98, 308-332; Peng. J. W., & Wagner, G. (1992b) Biochemistry 31, 8571-8586]. 15N spin-lattice relaxation [Rn(Nz)], spin-spin relaxation [Rn(Nx,y)], cross-relaxation [RN(Hz-->Nz)], two-spin order [RNH(2HzNz)], and antiphase [RNH(2HzNx,y)] rates were determined for 52 of the 65 backbone amide groups at 10 degrees C and ph 6.5 at 11.74 T. Calculations of the spectral density functions using a reduced set of RN(Nz),RN(Nx,y),RN(Hz-->Nz), and RNH(2HzNz) gave excellent agreement with those calculated using all six sets. The reduced method has the added advantage that the errant behavior seen at high field values is circumvented. A linear correlation was found between J(omega N) and J(0) with a limited and clearly defined range of J(0) values which defines the range of rates for internal motions in GAL4(1-65). It appears that all residues experience a combination of two movements: one of the overall tumbling (correlation time, 8.65 ns) and the other of fast internal fluctuations of the structure. The respective weights of these contributions vary with the primary sequence and faithfully mirror the secondary and tertiary elements of the protein. The position on the correlation line of J(omega N) versus J(0) indicates the amount of angular averaging relative to the overall motion of the protein. A spectral density function for internal motions can be described.

Amino Acid Sequence↗

PubMed1996

Local mobility within villin 14T probed via heteronuclear relaxation measurements and a reduced spectral density mapping.

Villin 14T, a representative domain from the actin severing and bundling protein villin, binds calcium ions and actin monomers. To begin to understand the contributions of mobility to the villin-calcium and villin-actin interactions, relaxation rates for magnetization involving the amide nitrogens and protons have been measured for 15N-labeled villin 14T in solution. Although we have measured the complete set of rates required for a full spectral density map, difficulties in the accurate measurement of relaxation rates for antiphase coherence and two-spin order led us to consider a reduced mapping formalism. From the reduced spectral density map, a model-free analysis, or directly from the measured Nx,y relaxation rates, local variations in mobility along the backbone of villin 14T have been revealed. Fast motions are evident not only at the amino and carboxyl termini but also in the turn between strands beta 4 and beta 5 of the central beta-sheet and in the turn between helix alpha 3 and strand beta 7. Slower motions are suggested for the turn between strands beta 2 and beta 3. Motions on the microsecond to millisecond time scale have been probed directly by examining the dependence of the proton transverse relaxation rate on the spin-locking field strength. Leu11 shows a strong dependence on field strength, implying conformational exchange with a time constant of 125 +/- 69 microseconds. The backbone at the actin-binding interface appears to be rather rigid.

Actins↗

PubMed1996