Biomedical subjects

P D Adams

Publications and source records attributed to P D Adams.

42 records · Page 3Linked to original sources

PubMed1995

Conformational variability in the refined structure of the chaperonin GroEL at 2.8 A resolution.

Improved refinement of the crystal structure of GroEL from Escherichia coli has resulted in a complete atomic model for the first 524 residues. A new torsion-angle dynamics method and non-crystallographic symmetry restraints were used in the refinement. The model indicates that conformational variability exists due to rigid-body movements between the apical and intermediate domains of GroEL, resulting in deviations from strict seven-fold symmetry. The regions of the protein involved in polypeptide and GroES binding show unusually high B factors; these values may indicate mobility or discrete disorder. The variability of these regions may play a role in the ability of GroEL to bind a wide variety of substrates.

Bacterial Proteins↗

PubMed1994

Deregulated transcription factor E2F-1 expression leads to S-phase entry and p53-mediated apoptosis.

E2F-1 is a transcription factor suspected of activating genes required for S phase and a known target for the action of RB, the retinoblastoma gene product. Its induction in quiescent fibroblasts led to S-phase entry followed by apoptosis. E2F-1-mediated apoptosis was suppressed by coexpression of wild-type RB or a transdominant negative mutant species of p53. In contrast, coexpression of a naturally occurring loss-of-function RB mutant or wild-type p53 did not suppress the induction of apoptosis under these conditions. Thus, deregulated E2F-1 activity gives rise to proliferative and apoptotic signals. p53 appears to participate in the execution of the latter.

Animals↗

PubMed1994

Structural organization of the pentameric transmembrane alpha-helices of phospholamban, a cardiac ion channel.

Phospholamban is a 52 amino acid calcium regulatory protein found as pentamers in cardiac SR membranes. The pentamers form through interactions between its transmembrane domains, and are stable in SDS. We have employed a saturation mutagenesis approach to study the detailed interactions between the transmembrane segments, using a chimeric protein construct in which staphylococcal nuclease (a monomeric soluble protein) is fused to the N-terminus of phospholamban. The chimera forms pentamers observable in SDS-PAGE, allowing the effects of mutations upon the oligomeric association to be determined by electrophoresis. The disruptive effects of amino acid substitutions in the transmembrane domain were classified as sensitive, moderately sensitive or insensitive. Residues of the same class lined up on faces of a 3.5 amino acids/turn helical projection, allowing the construction of a model of the interacting surfaces in which the helices are associated in a left-handed pentameric coiled-coil configuration. Molecular modeling simulations (to be described elsewhere in detail) confirm that the helices readily form a left-handed coiled-coil helical bundle and have yielded molecular models for the interacting surfaces, the best of which is identical to that predicted by the mutagenesis. Residues lining the pore show considerable structural sensitivity to mutation, indicating that care must be taken in interpreting the results of mutagenesis studies of channels. The cylindrical ion pore (minimal diameter of 2 A) appears to be defined largely by hydrophobic residues (I40, L43 and I47) with only two mildly polar elements contributed by sulfurs in residues C36 and M50.

Amino Acid Sequence↗

PubMed1994

A dimerization motif for transmembrane alpha-helices.

Specific helix-helix interactions inside lipid bilayers guide the folding and assembly of many integral membrane proteins and their complexes. We report here a pattern of 7 amino acids (LIxxGVxxGVxxT) which when introduced into several hydrophobic transmembrane alpha-helices promotes their specific dimerization. Dimerization is driven by interactions that are specific, dominated by the helix-helix interface, and involve no potentially ionizable groups. The motif may provide a useful tool for the functional analysis of such interactions in a variety of systems. Further, since this particular motif is rare, whilst specific helix association is not, many other such motifs may exist, which could permit sorting within complex membranes as well as guiding folding and oligomerization.

Amino Acid Sequence↗

PubMed1992

Activation of mitogen-activated protein (MAP) kinase by a MAP kinase-kinase.

Previously it has been shown that acute 12-O-tetradecanoylphorbol-13-acetate treatment of intact U937 cells results in activation of mitogen-activated protein (MAP) kinase and a MAP kinase activator. MAP kinase activator induces phosphorylation of MAP kinase on tyrosine and threonine residues, thereby activating MAP kinase. Here, experiments with the irreversible kinase inhibitor, 5'-p-fluorosulfonylbenzoyladenosine (FSBA), show that MAP kinase activator is in fact a MAP kinase-kinase. Treatment of MAP kinase activator with FSBA results in complete inactivation. This inactivation is prevented by a 10-fold excess of ATP. Inactivation of MAP kinase by FSBA does not affect the extent of threonine/tyrosine phosphorylation induced by MAP kinase-kinase.

Adenosine↗

PubMed1991

TPA-induced activation of MAP kinase.

Threonine and tyrosine residue phosphorylation of a 42 kDa protein identified as mitogen-activated protein kinase (MAP kinase) was stimulated in extracts from TPA-pretreated cells. It is further shown that TPA pretreatment leads to the enhancement of an activity that will induce reactivation of dephosphorylated/inactivated MAP kinase. This TPA-induced activity induces the threonine and tyrosine phosphorylation of p42 in extracts from unstimulated cells.

Amino Acid Sequence↗