Biomedical subjects

Alison Park

Publications and source records attributed to Alison Park.

3 recordsLinked to original sources

PubMed2006

Assessing cognitive function in cancer patients.

GOALS OF WORK: Some patients with cancer suffer cognitive impairment after chemotherapy. A brief, sensitive instrument is required to screen patients for cognitive impairment. In this study, we compare three possible screening instruments. MATERIALS AND METHODS: Cancer patients (n=31) who had received adjuvant chemotherapy within 2 years underwent cognitive evaluation on three occasions. Fluent English speakers (n=20) completed the High Sensitivity Cognitive Screen (HSCS), the computer-based Headminder and CogHealth, and the Functional Assessment of Cancer Therapy-cognitive function (FACT-COG) questionnaire. Patients not fluent in English (NESB) (n=11) performed CogHealth and Headminder. RESULTS: The patients were aged 31-65 years, and 94% were women with breast cancer. At baseline, 6 of 20 (30%) had moderate-severe cognitive impairment on HSCS, 17 of 31 (55%) had scores greater than one standard deviation (SD) below the mean for normative data in one to two of three domains on Headminder, and on CogHealth, 8 of 31 (26%) were greater than one SD below the mean in at least two of six domains. A large practice effect was seen for the HSCS, with moderate-severe cognitive impairment decreasing from 30 to 5% between the first and second assessment. On FACT-COG, 9 of 19 patients (47%) rated their cognition as greater than one SD below that of a pre-chemotherapy breast cancer control group, with impact on quality of life greater than one SD below for 10 of 19 (53%) patients. No correlation was seen between objective cognitive testing and the FACT-COG. CONCLUSIONS: CogHealth and Headminder were suitable for NESB patients. The HSCS is not recommended for longitudinal studies with short intervals between testing due to practice effect. There is poor correlation between the patients' perception of their cognitive impairment and the objective tests.

Adult↗

PubMed2004

Modulation of the ligand binding properties of the transcription repressor NmrA by GATA-containing DNA and site-directed mutagenesis.

NmrA is a negative transcription-regulating protein that binds to the C-terminal region of the GATA transcription-activating protein AreA. The proposed molecular mechanism of action for NmrA is to inhibit AreA binding to its target promoters. In contrast to this proposal, we report that a C-terminal fragment of AreA can bind individually to GATA-containing DNA and NmrA and that in the presence of a mixture of GATA-containing DNA and NmrA, the AreA fragment binds preferentially to the GATA-containing DNA in vitro. These observations are consistent with NmrA acting by an indirect route, such as by controlling entry into the nucleus. Deletion of the final nine amino acids of a C-terminal fragment of AreA does not affect NmrA binding. Wild-type NmrA binds NAD(+)(P+) with much greater affinity than NAD(P)H, despite the lack of the consensus GXXGXXG dinucleotide-binding motif. However, introducing the GXXGXXG sequence into the NmrA double mutant N12G/A18G causes an approximately 13-fold increase in the KD for NAD+ and a 2.3-fold increase for NADP+. An H37W mutant in NmrA designed to increase the interaction with the adenine ring of NAD+ has a decrease in KD of approximately 4.5-fold for NAD+ and a marginal 24% increase for NADP+. The crystal structure of the N12G/A18G mutant protein shows changes in main chain position as well as repositioning of H37, which disrupts contacts with the adenine ring of NAD+, changes which are predicted to reduce the binding affinity for this dinucleotide. The substitutions E193Q/D195N or Q202E/F204Y in the C-terminal domain of NmrA reduced the affinity for a C-terminal fragment of AreA, implying that this region of the protein interacts with AreA.

Base Sequence↗

PubMed2004

Biophysical and kinetic analysis of wild-type and site-directed mutants of the isolated and native dehydroquinate synthase domain of the AROM protein.

Dehydroquinate synthase (DHQS) is the N-terminal domain of the pentafunctional AROM protein that catalyses steps 2 to 7 in the shikimate pathway in microbial eukaryotes. DHQS converts 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) to dehydroquinate in a reaction that includes alcohol oxidation, phosphate beta-elimination, carbonyl reduction, ring opening, and intramolecular aldol condensation. Kinetic analysis of the isolated DHQS domains with the AROM protein showed that for the substrate DAHP the difference in Km is less than a factor of 3, that the turnover numbers differed by 24%, and that the Km for NAD+ differs by a factor of 3. Isothermal titration calorimetry revealed that a second (inhibitory) site for divalent metal binding has an approximately 4000-fold increase in KD compared to the catalytic binding site. Inhibitor studies have suggested the enzyme could act as a simple oxidoreductase with several of the reactions occurring spontaneously, whereas structural studies have implied that DHQS participates in all steps of the reaction. Analysis of site-directed mutants experimentally test and support this latter hypothesis. Differential scanning calorimetry, circular dichroism spectroscopy, and molecular exclusion chromatography demonstrate that the mutant DHQS retain their secondary and quaternary structures and their ligand binding capacity. R130K has a 135-fold reduction in specific activity with DAHP and a greater than 1100-fold decrease in the kcat/Km ratio, whereas R130A is inactive.

Alcohol Oxidoreductases↗