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Biomedical subjects

J Bennett

Publications and source records attributed to J Bennett.

At least 271 records · Page 15Linked to original sources
PubMed1989

A truncated analog of a pre-light-harvesting chlorophyll a/b protein II transit peptide inhibits protein import into chloroplasts.

It is unclear how transit peptides target nuclear-encoded precursor proteins to the chloroplast. This study establishes the feasibility of using synthetic peptides as competitive inhibitors of chloroplast protein import and as probes for the function of domains within transit peptides. We show that peptide pL(1-20), MAASTMALSSPAFAGKAVNY, an analog of the NH2 terminus of a pre-light harvesting chlorophyll a/b protein II from Arabidopsis, inhibits the import of several Arabidopsis and pea precursor proteins into pea chloroplasts. Inhibition occurs at a step between the initial binding of precursors to the chloroplast and the first proteolytic cleavage event and is not due to interference with ATP availability or chloroplast integrity. Presumably this reflects specific binding of the peptide to the import machinery in the chloroplast envelope. Our data are consistent with the suggestion (Karlin-Neumann, G. A., and Tobin, E. M. (1986) EMBO J. 5, 9-13) that two conserved blocks of amino acids near the NH2-terminus of transit peptides (spanned by peptide pL(1-20] participate in protein targeting. Computer analysis also shows peptide pL(1-20) lacks the amphiphilic properties characteristic of pre-sequences of many nuclear-encoded mitochondrial proteins. This shows a difference in the mechanisms for targeting proteins to chloroplasts and mitochondria.

Amino Acid Sequence↗
PubMed1989

Dominantly transmitted hematologic dysfunction clinically similar to Fanconi's anemia.

We report a family with a dominantly transmitted syndrome resembling Fanconi's anemia and spanning two generations. This syndrome was characterized by an ill-defined hematologic stem cell disorder, immune dysfunction, poor dentition, hyperpigmented skin, warts, and multiple second trimester spontaneous abortions and included one case of acute myelomonocytic leukemia (acute non-lymphocytic leukemia, M4). This family lacks the characteristic chromosomal aberrations of Fanconi's anemia. We believe this constellation of findings represents an entity not previously described.

Abortion, Habitual↗
PubMed1989

Age differences in the acculturation process.

Age differences were assessed in a conceptual model that seeks to explain how acculturation affects psychological well-being among Mexican Americans. The data were from a national probability sample of 859 persons of Mexican decent. It was hypothesized that low acculturation creates financial stress. Moreover, low acculturation and financial stress were in turn predicted to erode feelings of personal control and self-esteem. Finally, diminished feelings of control and low self-esteem were hypothesized to exert a negative impact on psychological well-being. When data from respondents of all ages was assessed, empirical support was found for all of the hypotheses except the linkage between acculturation and financial stress. However, few age differences emerged in the model. The authors conclude that older Mexican Americans may not be more vulnerable to the stressors associated with acculturation.

Acculturation↗
PubMed1989

Clinical audit--occurrence screening for QA.

The white paper says that within the next two years the Government would like to see all doctors taking part in medical audit. There are various ways in which an audit might be undertaken, and recently a pilot study was carried out in the Brighton district of a system which has been used effectively in the USA and Australia.

England↗
PubMed1989

The prevalence and risk of diabetic retinopathy among Indians of southwest Oklahoma.

The overall prevalence of diabetic retinopathy was 49.3% among 142 diabetic Indians examined at the Indian Health Service at Clinton, Oklahoma. Univariate analysis suggested a positive relationship between duration of diabetes and prevalence of retinopathy. This Indian diabetic population should be examined yearly for diabetic retinopathy.

Adult↗
PubMed1988

Localization of a 64-kDa phosphoprotein in the lumen between the outer and inner envelopes of pea chloroplasts.

The identification and localization of a marker protein for the intermembrane space between the outer and inner chloroplast envelopes is described. This 64-kDa protein is very rapidly labeled by [gamma-32P]ATP at very low (30 nM) ATP concentrations and the phosphoryl group exhibits a high turnover rate. It was possible to establish the presence of the 64-kDa protein in this plastid compartment by using different chloroplast envelope separation and isolation techniques. In addition comparison of labeling kinetics by intact and hypotonically lysed pea chloroplasts support the localization of the 64-kDa protein in the intermembrane space. The 64-kDa protein was present and could be labeled in mixed envelope membranes isolated from hypotonically lysed plastids. Mixed envelope membranes incorporated high amounts of 32P from [gamma-32P]ATP into the 64-kDa protein, whereas separated outer and inner envelope membranes did not show significant phosphorylation of this protein. Water/Triton X-114 phase partitioning demonstrated that the 64-kDa protein is a hydrophilic polypeptide. These findings suggest that the 64-kDa protein is a soluble protein trapped in the space between the inner and outer envelope membranes. After sonication of mixed envelope membranes, the 64-kDa protein was no longer present in the membrane fraction, but could be found in the supernatant after a 110,000 x g centrifugation.

Adenosine Triphosphate↗
PubMed1988

Tandem mass spectrometry reveals that three photosystem II proteins of spinach chloroplasts contain N-acetyl-O-phosphothreonine at their NH2 termini.

Photosystem II cores of spinach contain four phosphoproteins (8.3, 32, 34, and 44 kDa). Tryptic digestion of core particles released four phosphopeptides which were purified by affinity chromatography on Fe3+-chelating Sepharose and reverse-phase high pressure liquid chromatography. One peptide, derived from the 8.3-kDa protein, has been found to be the NH2 terminus of the psbH gene product (Michel, H. P., and Bennett, J. (1987) FEBS Lett. 212, 103-108). The other three peptides were found to be blocked at the NH2 terminus. We now report the use of tandem mass spectrometry to obtain the sequence of the three other peptides, to locate the phosphorylated residue, and to identify the blocking group. The three peptides correspond to the NH2 termini of D1, D2, and CPa-2; and each begins with N-acetyl-O-phosphothreonine. Comparison with sequences deduced from cloned genes indicates that D1 and D2 have lost their initiating N-formylmethionyl residues. The result for D1 contradicts the view that translation of D1 begins at the second AUG of the mRNA (Bloom, M., Brot, N., Cohen, B. N., and Weissbach, H. (1986) Methods Enzymol. 118, 309-315) and supports the view that processing of pre-D1 to its mature form involves loss of amino acids from the COOH terminus (Marder, J. B., Goloubinoff, P., and Edelman, M. (1984) J. Biol. Chem. 259, 3900-3908). In contrast, CPa-2 is processed at the NH2 terminus by cleaving off the first 14 amino acids. These results also establish that the NH2 termini of D1, D2, and CPa-2 are exposed to the stromal side of the thylakoids.

Amino Acid Sequence↗
PubMed1988

Cytochrome b6f complex is required for phosphorylation of light-harvesting chlorophyll a/b complex II in chloroplast photosynthetic membranes.

The light-harvesting chlorophyll a/b complex (LHC II) and four photosystem II (PS II) core proteins (8.3, 32, 34 and 44 kDa) become phosphorylated in response to reduction of the intersystem electron transport chain of green plant chloroplasts. Previous studies indicated that reduction of the plastoquinone (PQ) pool is the key event in kinase activation. However, we show here that, unlike PS II proteins, LHC II is phosphorylated only when the cytochrome b6f complex is active. Two lines of evidence support this conclusion. (1) 2,5-Dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) and the 2,4-dinitrophenyl ether of iodonitrothymol (DNP-INT), which are known to block electron flow into the cytochrome complex, selectively inhibit LHC II phosphorylation in spinach thylakoids. (2) The hcf6 mutant of maize, which contains PQ but lacks the cytochrome b6f complex, phosphorylates the four PS II proteins but fails to phosphorylate LHC II in vivo or in vitro.

Benzoquinones↗
PubMed1988

The assessment of a computer administered questionnaire in the differential diagnosis of asthma and chronic airflow limitation.

We have tested a computer administered respiratory symptom questionnaire in patients with asthma, chronic airflow limitation, and subjects with no evidence of respiratory disease. The questionnaire was highly effective at distinguishing patients with respiratory disease from those without. However, the responses of asthmatic patients and patients with CAL to the majority of questions were similar though the responses to four out of 11 questions were significantly different. We conclude that such a computer administered questionnaire is of limited value in distinguishing patients with asthma and CAL, underlining the importance of objective tests in this differential diagnosis.

Adult↗
PubMed1988

Helping people with AIDS live well at home.

Responding to AIDS as a chronic, multisystem disease means emphasizing quality of life as the chief goal throughout its course. By mobilizing and supporting the strengths of the individual and his/her social network, the homecare nurse allows the person with AIDS or ARC to focus his/her energy on being well, not the disease. Meeting the challenge requires commitment, creativity, collaboration, and compassion.

AIDS-Related Complex↗
PubMed1987

Light-dependent accumulation and localization of photosystem II proteins in maize.

We have raised antibodies against several major components of photosystem II. These antisera, which are directed against the apoproteins of two chlorophyll-binding proteins (CPa-1 and CPa-2), the apoprotein of light-harvesting complex II and the 33-kDa extrinsic protein of the oxygen-evolving complex, were used to examine the light regulation of photosystem II assembly in maize. The principal findings of this study are as follows. The 33-kDa protein is present in dark-grown maize and the content increases 5-10-fold upon illumination. The level of the protein is mediated at least in part by phytochrome and is independent of the accumulation of chlorophyll. In contrast, none of the three chlorophyll-binding proteins examined was detectable in leaves of maize grown in darkness or under other light regimes where chlorophyll does not accumulate. Even in the absence of photosystem II assembly, the 33-kDa protein is properly transported across the thylakoid into the lumen. However, the protein does not attach in the normal way to the inner surface of the membrane under these conditions.

Biological Transport↗