Biomedical subjects

K L Wick

Publications and source records attributed to K L Wick.

4 recordsLinked to original sources

PubMed2001

A new molecular target of insulin action: regulating the pivotal PDK1.

Over the last several years, a great level of interest has rallied behind understanding how the pivotal kinase, 3'-phosphoinositide dependent kinase 1 (PDK1) is regulated. PDK1 phosphorylates and activates members of the AGC kinase family shown to be activated downstream of phosphoinositide 3-kinase (P13K); however, the functional dependency of PDK1 on P13K for activation of its targets is less clear. The P13K signaling pathway mediates numerous cellular responses upon growth factor and hormone stimulation. Specifically, P13K signaling influences many of the metabolic and mitogenic functions of the anabolic hormone, insulin. Thus, the regulation of P13K and its downstream targets by insulin has become an important topic for investigation. Given its central role as the kinase upstream of those signaling pathways linked to P13K, the regulation of PDK1 by insulin and other factors is at the height of many of these investigations. Current theories on PDK1 regulation propose substrate conformation and subcellular localization as the primary mediators of PDK1 function. The array of PDK1 substrates suggests, however, that in cells PDK1 may be more tightly regulated. Recent data support phosphorylation as a potential regulatory mechanism that may play an additional role in directing the specificity of PDK1 towards its physiological substrates. The combination of these regulatory mechanisms along with the potential for multiple PDK1 isoforms with select tissue distribution may contribute to the diversified actions of insulin signaling. The targeting of these various aspects of PDK1 regulation may provide for novel therapeutic treatments for diseases such as diabetes and cancer.

3-Phosphoinositide-Dependent Protein Kinases↗

PubMed1991

Interactions between lac repressor protein and site-specific bromodeoxyuridine-substituted operator DNA. Ultraviolet footprinting and protein-DNA cross-link formation.

Specific contacts between the lac repressor and operator have been explored using 5-bromodeoxyuridine-substituted DNA. Substitution of BrdU for single thymidine positions in a synthetic 40-base pair operator provides substrate for ultraviolet irradiation; upon irradiation, strand scission occurs at the BrdU residues. When bound, lac repressor protein provides protection against UV-induced breakage depending on the nature of the sites and type of interaction. We have confirmed 13 unique sites of inducer-sensitive protection along the operator sequence using this method compared to complete substitution with BrdU; differences were observed at two positions for singly substituted versus completely substituted DNAs (Ogata, R., and Gilbert, W. (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 4973-4976). The ability of these photosensitive DNAs to form short range cross-links to bound protein has been used to determine the efficiency with which cross-linked protein-DNA complexes are generated at each individual site of BrdU substitution. Five sites of high efficiency cross-linking to the repressor protein have been identified. At one site, cross-linking without protection from strand scission was observed; this result suggests an unusual mechanism of strand scission and/or cross-linking at this site. Comparison of the UV protection results and the cross-linking data show that these processes provide complementary tools for identifying and analyzing individual protein-DNA contacts.

Autoradiography↗

PubMed1991

Identification of amino acids in lac repressor protein cross-linked to operator DNA specifically substituted with bromodeoxyuridine.

Amino acids in lac repressor protein which form cross-links to lac operator DNA specifically substituted with bromodeoxyuridine (BrdU) have been identified. Five sites of cross-linking in BrdU-substituted operator DNA were found at positions +3, +4, +14, +18, and +19 relative to the initiation site for transcription (Wick, K.L., and Matthews, K.S. (1991) J. Biol. Chem. 266, 6106-6112). Irradiation of complexes of repressor and each of these five singly substituted operator DNAs was executed under large scale conditions to generate sufficient complex for proteolysis, separation of the peptide-DNA, and peptide sequencing. The DNAs substituted with BrdU for thymidine at positions +3, +18, and +19 yielded cross-links to the peptide spanning residues 23-33, with the cross-link identified at His-29. Substitution at position +14 resulted in a cross-link to Tyr-17 within the peptide containing amino acids 13-22. These results are consistent with the structure determined by NMR and molecular dynamics calculations of the NH2-terminal headpiece-symmetric operator complex (Lamerichs, R.M.J.N., Boelens, R., van der Marel, G.A., van Boom, J.H., Kaptein, R., Buck, F., Fera, B., and Rüterjans, H. (1989) Biochemistry 28, 2895-2991; de Vlieg, J., Berendsen, H.J.C., and van Gunsteren, W.F. (1989) Proteins 6, 104-127). This structure indicates proximity of His-29 in the major groove to thymidines at positions +3 and +4. Since base pairs at positions +18 and +19 occupy symmetrical positions to +3 and +4 in the promoter distal region of the operator, it would be anticipated that cross-links similar to the +3 and +4 positions would form at these sites; this prediction is not borne out by the behavior at +4/+18, as no peptide could be identified cross-linked to DNA substituted at +4. Molecular dynamics simulations and the NMR data indicate that Tyr-17 interacts with the thymine at position +8, which is symmetrically related to position +14. Although BrdU-associated strand scission at +8 is protected, this site does not cross-link with bound lac repressor; inversely, DNA substituted with BrdU at +14 cross-links to repressor, but is not protected from strand scission by the presence of the protein. These differences at symmetrically related nucleotide positions (+4 versus +18, +8 versus +14) reflect the inherent asymmetry in the interaction. The identification of amino acids in proximity to specifically substituted sites confirms that positions of several amino acids in the intact protein-operator complex correspond to those in the structure of the NH2-terminal headpiece-operator DNA complex.

Amino Acid Sequence↗

PubMed1990

Seminal plasma anti-sperm antibodies and IVF: the effect of semen sample collection into 50% serum.

A retrospective analysis was carried out which studied IVF results for couples in whom the male partner had anti-sperm antibodies in seminal plasma, as judged by a positive MAR test. Of the 59 couples studied over a total of 113 cycles, 30 had IVF semen samples collected into sterile, dry pots. Thirty-eight of the couples had samples collected into medium containing 50% serum, and nine couples underwent separate treatment cycles with samples collected both dry and into 50% serum. The results demonstrate that the addition of serum to sample collection pots significantly improves the oocyte fertilization rate and is followed by a greater chance of conception for these couples.

Antibodies↗