scholarly journals The fox Operon from Rhodobacter Strain SW2 Promotes Phototrophic Fe(II) Oxidation in Rhodobacter capsulatus SB1003

2006 ◽  
Vol 189 (5) ◽  
pp. 1774-1782 ◽  
Author(s):  
Laura R. Croal ◽  
Yongqin Jiao ◽  
Dianne K. Newman
Keyword(s):  
Molecular Basis ◽  
Rhodobacter Capsulatus ◽  
Maximal Activity ◽  
Pyrroloquinoline Quinone ◽  
Oxygenic Photosynthesis ◽  
Transport Function ◽  
Significant Similarity ◽  
Oxidation Activity ◽  
Biochemical Studies ◽  
And Function

ABSTRACT Anoxygenic photosynthesis based on Fe(II) is thought to be one of the most ancient forms of metabolism and is hypothesized to represent a transition step in the evolution of oxygenic photosynthesis. However, little is known about the molecular basis of this process because, until recently (Y. Jiao and D. K. Newman, J. Bacteriol. 189:1765-1773, 2007), most phototrophic Fe(II)-oxidizing bacteria have been genetically intractable. In this study, we circumvented this problem by taking a heterologous-complementation approach to identify a three-gene operon (the foxEYZ operon) from Rhodobacter sp. strain SW2 that confers enhanced light-dependent Fe(II) oxidation activity when expressed in its genetically tractable relative Rhodobacter capsulatus SB1003. The first gene in this operon, foxE, encodes a c-type cytochrome with no significant similarity to other known proteins. Expression of foxE alone confers significant light-dependent Fe(II) oxidation activity on SB1003, but maximal activity is achieved when foxE is expressed with the two downstream genes foxY and foxZ. In SW2, the foxE and foxY genes are cotranscribed in the presence of Fe(II) and/or hydrogen, with foxZ being transcribed only in the presence of Fe(II). Sequence analysis predicts that foxY encodes a protein containing the redox cofactor pyrroloquinoline quinone and that foxZ encodes a protein with a transport function. Future biochemical studies will permit the localization and function of the Fox proteins in SW2 to be determined.

Molecular basis of ovarian development and function

2002 ◽  
Vol 7 (1-3) ◽  
pp. d2006 ◽  
Author(s):  
Barbara Vanderhyden
Keyword(s):  
Molecular Basis ◽  
Ovarian Development ◽  
And Function

scholarly journals Antioxidant and Signaling Role of Plastid-Derived Isoprenoid Quinones and Chromanols

2021 ◽  
Vol 22 (6) ◽  
pp. 2950
Author(s):  
Beatrycze Nowicka ◽  
Agnieszka Trela-Makowej ◽  
Dariusz Latowski ◽  
Kazimierz Strzalka ◽  
Renata Szymańska
Keyword(s):  
Current Knowledge ◽  
Stress Factors ◽  
Oxygenic Photosynthesis ◽  
Ros Generation ◽  
Main Site ◽  
Storage Lipids ◽  
Abiotic Stress Factors ◽  
Cell Components ◽  
And Function

Plant prenyllipids, especially isoprenoid chromanols and quinols, are very efficient low-molecular-weight lipophilic antioxidants, protecting membranes and storage lipids from reactive oxygen species (ROS). ROS are byproducts of aerobic metabolism that can damage cell components, they are also known to play a role in signaling. Plants are particularly prone to oxidative damage because oxygenic photosynthesis results in O2 formation in their green tissues. In addition, the photosynthetic electron transfer chain is an important source of ROS. Therefore, chloroplasts are the main site of ROS generation in plant cells during the light reactions of photosynthesis, and plastidic antioxidants are crucial to prevent oxidative stress, which occurs when plants are exposed to various types of stress factors, both biotic and abiotic. The increase in antioxidant content during stress acclimation is a common phenomenon. In the present review, we describe the mechanisms of ROS (singlet oxygen, superoxide, hydrogen peroxide and hydroxyl radical) production in chloroplasts in general and during exposure to abiotic stress factors, such as high light, low temperature, drought and salinity. We highlight the dual role of their presence: negative (i.e., lipid peroxidation, pigment and protein oxidation) and positive (i.e., contribution in redox-based physiological processes). Then we provide a summary of current knowledge concerning plastidic prenyllipid antioxidants belonging to isoprenoid chromanols and quinols, as well as their structure, occurrence, biosynthesis and function both in ROS detoxification and signaling.

Effect of acidosis on PTH-dependent renal adenylate cyclase in phosphorus deprivation: role of G proteins

1990 ◽  
Vol 258 (6) ◽  
pp. F1640-F1649
Author(s):  
E. Bellorin-Font ◽  
R. Starosta ◽  
C. L. Milanes ◽  
C. Lopez ◽  
N. Pernalete ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Adenylate Cyclase ◽  
Maximal Activity ◽  
Phosphate Deprivation ◽  
Adp Ribosylation ◽  
Phosphate Depletion ◽  
Cortical Membranes ◽  
And Function ◽  
Gs Alpha

These studies examine the regulation of adenylate cyclase in renal cortical membranes from phosphate-deprived and phosphate-deprived acidotic dogs. Enzyme stimulation by parathyroid hormone (PTH) was decreased in phosphate deprivation [Vmax 1,578 +/- 169 vs. 2,581 +/- 219 pmol adenosine 3',5'-cyclic monophosphate (cAMP).mg protein-1 x 30 min-1 in controls, P less than 0.01]. Metabolic acidosis further decreased PTH-stimulated activity. Membranes from phosphate-deprived dogs showed a decrease in Gs alpha-content by cholera toxin-dependent ADP-ribosylation (174 +/- 18 arbitrary units vs. 266.4 +/- 13.6 in controls, P less than 0.01). Metabolic acidosis further decreased Gs alpha-content, P less than 0.01. Gi content by pertussis-dependent ADP-ribosylation was also lower in phosphate-deprived and phosphate-deprived acidotic animals. Gs function was examined by its property to protect the catalytic unit from inactivation by N-ethylmaleimide when preincubated with GTP gamma S. In controls, protection of inactivation was 80% of the maximal activity, whereas in phosphate deprivation protection was less than 50%. In conclusion, metabolic acidosis enhances adenylate cyclase resistance to PTH in phosphate deprivation. These alterations are associated with a decrease in the content and function of Gs alpha, suggesting a role of Gs in the renal adaptation to phosphate depletion and acidosis.

The effects of Acute and Chronic β-Adrenoceptor Blockade on the Myofibrillar Contractile System in the Dog Heart

1984 ◽  
Vol 67 (2) ◽  
pp. 259-267 ◽  
Author(s):  
M. K. Davies ◽  
P. Cummins ◽  
W. A. Littler
Keyword(s):  
Calcium Sensitivity ◽  
Maximal Activity ◽  
Biopsy Specimens ◽  
Contractile System ◽  
Chronic Therapy ◽  
Before And After ◽  
Adaptive Effect ◽  
Electrophoretic Techniques ◽  
Myocardial Contractile ◽  
And Function

1. Electrophoretic and enzyme techniques have been used to study the structure and function of the contractile protein system in the myocardium of dogs before and after β-adrenoceptor blockade. Animals were examined after acute β-adrenoceptor blockade by using intravenous atenolol (0.2 mg/kg) and following chronic therapy with oral atenolol (100 mg twice daily) for a mean period of 106 days. 2. Two-dimensional polyacrylamide-gel electrophoretic techniques were used to examine the myocardial contractile and regulatory proteins present in endomyocardial biopsy specimens obtained after acute and chronic β-adrenoceptor blockade. No differences in charge, molecular weight or the relative proportions of actin, myosin light chains, tropomyosin or troponin-C were seen after either acute or chronic β-adrenoceptor blockade. 3. The maximal activity and calcium sensitivity of the myofibrillar adenosine triphosphatase (ATPase) was also unchanged after acute and chronic atenolol therapy. 4. It is concluded that β-adrenoceptor blockade has no significant adaptive effect on the structural or functional properties of the myofibril.

scholarly journals Cytological and Biochemical Studies of Anucleolate Xenopus Larvae

1962 ◽  
Vol s3-103 (61) ◽  
pp. 25-35
Author(s):  
H. WALLACE
Keyword(s):  
Alkaline Phosphatase ◽  
Nucleic Acid ◽  
Acid Content ◽  
Deoxyribonucleic Acid ◽  
Nucleic Acid Content ◽  
Tail Bud ◽  
Lethal Mutant ◽  
Cytoplasmic Rna ◽  
Biochemical Studies ◽  
And Function

A larval lethal mutant of Xenopus laevis lacks true nucleoli but possesses analogous intranuclear organelles, here termed blobs, which are smaller and more numerous than nucleoli. Cytochemical tests reveal that blobs (like nucleoli) contain ribonucleic acid (RNA), arginine, and alkaline phosphatase, but probably no Feulgen-positive material. Anucleolate larvae are deficient in cytoplasmic RNA. By biochemical methods the nucleic acid content of anucleolate embryos is found to be normal at the tail-bud stage, but does not increase after this. By the time they hatch, anucleolate larvae are deficient in both RNA and deoxyribonucleic acid (DNA). The implications of this and related mutations on the formation and function of the nucleolus are considered. The term ‘blob’ is justified in that it would be misleading to regard such organelles as nucleoli produced by normally latent organizers.

scholarly journals Rewiring of an ancestral Tbx1/10-Ebf-Mrf network for pharyngeal muscle specification in distinct embryonic lineages

2016 ◽  
Author(s):  
Theadora Tolkin ◽  
Lionel Christiaen
Keyword(s):  
Molecular Basis ◽  
Skeletal Muscles ◽  
Temporal Order ◽  
Regulatory Factor ◽  
Pharyngeal Muscle ◽  
Linear Cascade ◽  
Founder Cells ◽  
Muscle Groups ◽  
And Function

Skeletal muscles arise from diverse embryonic origins, yet converge on common regulatory programs involving muscle regulatory factor (MRF)-family genes. Here, we compare the molecular basis of myogenesis in two separate muscle groups in the simple chordate Ciona: the atrial and oral siphon muscles. Here, we describe the ontogeny of OSM progenitors and characterize the clonal origins of OSM founders to compare mechanisms of OSM specification to what has been established for ASM. We determined that, as is the case in the ASM, Ebf and Tbx1/10 are both expressed and function upstream of Mrf in the OSM founder cells. However, regulatory relationships between Tbx1/10, Ebf and Mrf differ between the OSM and ASM lineages: while Tbx1/10, Ebf and Mrf form a linear cascade in the ASM, Ebf and Tbx1/10 are expressed in the inverse temporal order and are required together in order to activate Mrf in the OSM founder cells.

Characterization of transport mechanisms and determinants critical for Na+-dependent Pisymport of the PiT family paralogs human PiT1 and PiT2

2006 ◽  
Vol 291 (6) ◽  
pp. C1377-C1387 ◽  
Author(s):  
Pernille Bøttger ◽  
Susanne E. Hede ◽  
Morten Grunnet ◽  
Boy Høyer ◽  
Dan A. Klærke ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Divalent Cations ◽  
Maximal Activity ◽  
Xenopus Laevis Oocytes ◽  
Transport Function ◽  
Knockout Mutant ◽  
Uptake Medium ◽  
The Impact ◽  
First Time

The general phosphate need in mammalian cells is accommodated by members of the Pitransport (PiT) family ( SLC20), which use either Na+or H+to mediate inorganic phosphate (Pi) symport. The mammalian PiT paralogs PiT1 and PiT2 are Na+-dependent Pi(NaPi) transporters and are exploited by a group of retroviruses for cell entry. Human PiT1 and PiT2 were characterized by expression in Xenopus laevis oocytes with32Pias a traceable Pisource. For PiT1, the Michaelis-Menten constant for Piwas determined as 322.5 ± 124.5 μM. PiT2 was analyzed for the first time and showed positive cooperativity in Piuptake with a half-maximal activity constant for Piof 163.5 ± 39.8 μM. PiT1- and PiT2-mediated Na+-dependent Piuptake functions were not significantly affected by acidic and alkaline pH and displayed similar Na+dependency patterns. However, only PiT2 was capable of Na+-independent Pitransport at acidic pH. Study of the impact of divalent cations Ca2+and Mg2+revealed that Ca2+was important, but not critical, for NaPitransport function of PiT proteins. To gain insight into the NaPicotransport function, we analyzed PiT2 and a PiT2 Pitransport knockout mutant using22Na+as a traceable Na+source. Na+was transported by PiT2 even without Piin the uptake medium and also when Pitransport function was knocked out. This is the first time decoupling of Pifrom Na+transport has been demonstrated for a PiT family member. Moreover, the results imply that putative transmembrane amino acids E55and E575are responsible for linking Piimport to Na+transport in PiT2.

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