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Biomedical subjects

M Potts

Publications and source records attributed to M Potts.

At least 19 recordsLinked to original sources
PubMed1997

Protein tyrosine phosphorylation in the cyanobacterium Anabaena sp. strain PCC 7120.

Components of a protein tyrosine phosphorylation/dephosphorylation network were identified in the cyanobacterium Anabaena sp. strain PCC 7120. Three phosphotyrosine (P-Tyr) proteins of 27, 36, and 52 kDa were identified through their conspicuous immunoreactions with RC20H monoclonal antibodies specific for P-Tyr. These immunoreactions were outcompeted completely by free P-Tyr (5 mM) but not by phosphoserine or phosphothreonine. The P-Tyr content of the three major P-Tyr proteins and several minor proteins increased with their time of incubation in the presence of Mg-ATP and the protein phosphatase inhibitors sodium orthovanadate and sodium fluoride. Incubation of the same extracts with [gamma-32P]ATP but not [alpha-32P]ATP led to the phosphorylation of five polypeptides with molecular masses of 20, 27, 52, 85, and 100 kDa. Human placental protein tyrosine phosphatase 1B, with absolute specificity for P-Tyr, liberated significant quantities of 32Pi from four of the polypeptides, confirming that a portion of the protein-bound phosphate was present as 32P-Tyr. Alkaline phosphatase and the dual-specificity protein phosphatase IphP from the cyanobacterium Nostoc commune UTEX 584 also dephosphorylated these proteins and did so with greater apparent efficiency. Two of the polypeptides were partially purified, and phosphoamino analysis identified 32P-Tyr, [32P]phosphoserine, and [32P]phosphothreonine. Anabaena sp. strain PCC 7120 cell extracts contained a protein tyrosine phosphatase activity that was abolished in the presence of sodium orthovanadate and inhibited significantly by the sulfhydryl-modifying agents p-hydroxymercuriphenylsulfonic acid and p-hydroxymercuribenzoate as well as by heparin. In Anabaena sp. strain PCC 7120 the presence and/or phosphorylation status of P-Tyr proteins was influenced by incident photon flux density.

Anabaena↗
PubMed1997

Protein-tyrosine phosphorylation in the Archaea.

Sulfolobus sulfataricus ATCC 35091, Haloferax volcanii, and Methanosarcina thermophila TM-1, representing the Euryarchaeota and Crenarchaeota subdomains of the Archaea, contain proteins which are phosphorylated on tyrosine. These data raise fundamental questions as to the origin and evolution of tyrosine phosphorylation, a protein modification that is of pivotal importance in the regulation of the physiology of eukaryotic cells.

Archaea↗
PubMed1996

Abortion and fertility regulation.

To achieve their desired fertility, women use a combination of contraception and abortion, and some societies also place constraints on marriage and sexual activity. The degree to which these means are adopted varies considerably, but for the foreseeable future abortion will remain an important element of fertility regulation. Globally, complications of unsafe abortion affect hundreds of thousands of women each year, and account for as many as 100,000 deaths annually (about two in ten maternal deaths), mainly in poor countries, where abortion typically remains illegal. Access to safe abortion is both essential and technically feasible and should be provided in combination with good quality family planning services.

Abortion, Illegal↗
PubMed1996

Substrate specificity of IphP, a cyanobacterial dual-specificity protein phosphatase with MAP kinase phosphatase activity.

The substrate specificity of the cyanobacterial dual-specificity protein phosphatase, IphP, was explored using a variety of potential substrates. The enzyme displayed phosphomonoesterase activity toward a broad range of peptide, protein, and low molecular weight organophosphate compounds. It displayed little or no hydrolase activity toward phosphodiesters, phosphoramides, carboxyl esters, or sulfoesters. However, it did display measurable pyrophosphatase activity, especially toward ADP and ATP. Among the low molecular weight phosphomonoesters, the presence of an aromatic ring either as part of the leaving group alcohol or immediately adjacent thereto, as in 5'-AMP, was a strong positive determinant for hydrolysis. Among peptide and protein substrates, a rough, but imperfect, correlation between charge character and hydrolysis was noted in which proteins and phosphorylation sites of an acidic nature seemed favored. Heparin affected IphP activity in a substrate-dependent manner. Toward small organophosphates, heparin had no significant effect, but it was inhibitory toward most protein and peptide substrates. However, toward phosphoseryl casein and MAP kinase, it enhanced activity as much as 10-fold. This enhancement was attributed to the ability of heparin to bind to these substrate proteins, as well as IphP, and recruit them to the same microenvironment.

Adenosine Diphosphate↗
PubMed1996

Spectroscopical and functional characterization of the hemoglobin of Nostoc commune (UTEX 584 (Cyanobacterial).

Structural analysis of a monomeric hemoglobin from the cyanobacterium Nostoc commune strain UTEX 584, cyanoglobin (Potts et al. (1992) Science 256, 1690-1692), is presented. Cyanoglobin binds molecular oxygen reversibly, with high oxygen affinity and non-cooperativity. There was no evidence for decreased stability of the pigment at 37 degrees C. Cyanoglobin-specific antibodies showed no cross-reactivity with two reference hemoglobins, leghemoglobin a and sperm whale myoglobin. The absorption spectral properties of cyanoglobin differ significantly from those of the two reference hemoglobins. The spectrum of oxy-cyanoglobin most closely resembles that of an oxy-hemoglobin from the protozoan Tetrahymena pyriformis, a hemoprotein that shares substantial amino-acid sequence identity with cyanoglobin. Met-cyanoglobin possesses spectral characteristics at pH 7.0-9.0 that resemble those of the alkaline met-hemoglobin (a putative hemichrome) of another protozoan, Paramecium caudatum. The spin-state character of met-cyanoglobin is pH-dependent. Met-cyanoglobin does not coordinate the strong-field ligands, cyanide and azide, at pH 7.0. The capacity of cyanoglobin to coordinate cyanide increased with decreasing pH. Far-UV CD spectra of cyanoglobin are indicative of a protein with a significant amount of alpha-helical structure. Data from Soret-region CD spectra suggest that the orientations of the heme moieties in cyanoglobin and leghemoglobin a are similar to one another.

Blotting, Western↗
PubMed1996

The fertility transition in Cuba and the Federal Republic of Korea: the impact of organised family planning.

South Korea and Cuba are dissimilar in religion, economy, culture and attitudes toward premarital sexual relations. In 1960, Korea instituted a national family planning programme to combat rapid population growth. Cuba explicitly rejected Malthusian policies, but made family planning universally available in 1974 in response to health needs. Both countries have undergone rapid fertility declines and today have less than replacement level fertility. Both countries have also used a similar mixture of methods, including a high prevalence of female sterilisation. Abortion has played a major role in the fertility decline of both countries, rising in the first half of the fertility transition and then falling, although remaining a significant variable in the second half. It is concluded that access to contraception, voluntary sterilisation, and safe abortion has a direct impact on fertility and has been associated with a rapid fall in family size in two very different countries.

Birth Rate↗
PubMed1996

Fancy meeting you here! A fresh look at "prokaryotic" protein phosphorylation.

Bacteria play host to a wide range of protein phosphorylation-dephosphorylation systems (Fig. 1). As little as five years ago the known systems were thought to be late-emerging and absolutely prokaryote specific. Today we know that most protein kinases and protein phosphatases are descended from a set of common, and possibly quite ancient, prototypes. Prokaryote- and eukaryote-specific protein kinases and protein phosphatases are rare and represent exceptions, not the rule as previously thought. Commonality suggests that a dynamic and versatile regulatory mechanism was first adapted to the modulation of protein function as early if not earlier than more "basic" mechanisms such as allosterism, etc. The existence of common molecular themes confirms that the microbial world offers a unique, largely untapped library and a powerful set of tools for the understanding of a regulatory mechanism which is crucial to all organisms, tools whose diversity and experimental malleability will provide new avenues for exploring and understanding key modes of cellular regulation.

Animals↗
PubMed1996

GlbN (cyanoglobin) is a peripheral membrane protein that is restricted to certain Nostoc spp.

The glbN gene of Nostoc commune UTEX 584 is juxtaposed to nifU and nifH, and it encodes a 12-kDa monomeric hemoglobin that binds oxygen with high affinity. In N. commune UTEX 584, maximum accumulation of GlbN occurred in both the heterocysts and vegetative cells of nitrogen-fixing cultures when the rate of oxygen evolution was repressed to less than 25 micromol of O2 mg of chlorophyll a(-1) h(-1). Accumulation of GlbN coincided with maximum synthesis of NifH and ferredoxin NADP+ oxidoreductase (PetH or FNR). A total of 41 strains of cyanobacteria, including 40 nitrogen fixers and representing 16 genera within all five sections of the cyanobacteria were screened for the presence of glbN or GlbN. glbN was present in five Nostoc strains in a single copy. Genomic DNAs from 11 other Nostoc and Anabaena strains, including Anabaena sp. strain PCC 7120, provided no hybridization signals with a glbN probe. A constitutively expressed, 18-kDa protein which cross-reacted strongly with GlbN antibodies was detected in four Anabaena and Nostoc strains and in Trichodesmium thiebautii. The nifU-nifH intergenic region of Nostoc sp. strain MUN 8820 was sequenced (1,229 bp) and was approximately 95% identical to the equivalent region in N. commune UTEX 584. Each strand of the DNA from the nifU-nifH intergenic regions of both strains has the potential to fold into secondary structures in which more than 50% of the bases are internally paired. Mobility shift assays confirmed that NtcA (BifA) bound a site in the nifU-glbN intergenic region of N. commune UTEX 584 approximately 100 bases upstream from the translation initiation site of glbN. This site showed extensive sequence similarity with the promoter region of glnA from Synechococcus sp. strain PCC 7942. In vivo, GlbN had a specific and prominent subcellular location around the periphery of the cytosolic face of the cell membrane, and the protein was found solely in the soluble fraction of cell extracts. Our hypothesis is that GlbN scavenges oxygen for and is a component of a membrane-associated microaerobically induced terminal cytochrome oxidase.

Aerobiosis↗
PubMed1995

Safety implications of transferring the oral contraceptive from prescription-only to over-the-counter status.

The idea of making oral contraceptives available without prescription has a long history, and has been recently revived in the US and the UK. High dose oral contraceptives have generally been replaced by low dose formulations and, subsequently, most cardiovascular risks have been reduced and a protection against ovarian and uterine cancers has been consistently demonstrated. Oral contraceptive compliance, however, continues to be a problem, but there is no reason to assume that wise practice would be any more or less if oral contraceptives were available over-the-counter (OTC). Some countries have introduced alternatives to prescription-only oral contraceptives, whereby nurses, midwives, social workers and/or pharmacists are incorporated into the distribution process. This article concludes that the balance of risks and benefits is in favour of OTC access for oral contraceptives.

Contraceptives, Oral↗
PubMed1994

Analysis of the sequences within and flanking the cyanoglobin-encoding gene, glbN, of the cyanobacterium Nostoc commune UTEX 584.

A 3.5-kb segment of DNA containing nifU glbN nifH nifD was cloned from a gene library of Nostoc 584 and sequenced. The nifU-glbN intergenic region contains short tandemly repeated repetitive sequences (5'-AATTACG). A sequence corresponding to a NifA-like upstream activator sequence (with the consensus recognition sequence for BifA in Anabaena 7120), elements of a nifH promoter and a sequence that may function as a transcription terminator, were identified downstream from glbN. GlbN, unique to certain Nostoc spp., is more homologous to protozoan myoglobins than to any other prokaryotic, vertebrate or plant globins.

Amino Acid Sequence↗
PubMed1994

Water stress proteins of Nostoc commune (Cyanobacteria) are secreted with UV-A/B-absorbing pigments and associate with 1,4-beta-D-xylanxylanohydrolase activity.

Acidic water stress polypeptides (Wsp) with molecular masses of 33, 37 and 39 kDa are the most abundant soluble proteins in the cyanobacterium Nostoc commune. Wsp polypeptides and UV-A/B-absorbing pigments are secreted by cells, accumulate in the extracellular glycan sheath, and are released from desiccated colonies upon rehydration. No evidence was obtained for either glycosylation, phosphorylation, or acylation of Wsp polypeptides. NH2-terminal amino acid sequences of the 33-, 37-, and 39-kDa polypeptides were identical: Ala-Leu-Tyr-Gly-Tyr-Thr-Ile-Gly-Glu-Gln-X-Ile-Gln-Asn-Pro-Ser-Asn- Pro-Ser-Asn-Gly-Lys-Gln. This consensus NH2-terminal sequence and an internal sequence (Glu-Ala-Arg-Val-Thr-Gly-Pro-Thr-Thr-Pro-Ile-Asp) showed homologies with the sequences of carbohydrate-modifying enzymes. Purified Wsp polypeptides associate with a 1,4-beta-D-xylanxylanohydrolase activity that was inhibited specifically by Wsp antiserum. In the absence of salt, Wsp polypeptides, and the water-soluble UV-A/B-absorbing pigments, form multimeric complexes through strong ionic interactions. A possible role is suggested for Wsp polypeptides in the synthesis and/or modification of a xylose-containing UV-A/B-absorbing pigment.

Amino Acid Sequence↗