Osteoprotegerin is secreted into the coronary circulation: a possible association with the renin-angiotensin system and cardiac hypertrophy

The circulating osteoprotegerin (OPG) level reflects a series of cardiovascular diseases; however, the source(s) of circulating OPG remain(s) to be determined. This study explored whether OPG is released in the coronary circulation and whether it is associated with cardiac structure and function. Fifty-six patients (67±10 years old, male 57%, hypertension 73%, coronary artery disease 50%) were enrolled, and blood samples were collected simultaneously from the orifice of the left coronary artery (CA) and the coronary sinus (CS) after angiography. The concentration of OPG was higher in the CS than in the CA (7.7±4.1 vs. 6.7±3.6 pmol/l, p<0.001). The trans-cardiac OPG concentration was significantly (p=0.019) decreased in patients who have been prescribed either an angiotensin converting enzyme inhibitor or an angiotensin II type 1 receptor blocker (ACEI/ARB). In patients subgroup who did not take an ACEI/ARB (n=27), the trans-cardiac OPG level was positively correlated with age (r=0.396, p=0.041) and relative wall thickness of left ventricle (r=0.534, p=0.004). In multivariate linear regression analysis, relative wall thickness remained to be the independent variable for the trans-cardiac OPG level (p=0.004). Moreover, trans-cardiac OPG was significantly (p=0.021) increased in patients with relative wall thickness greater than 0.45 but it did not differ if the left ventricular mass index was increased (≥116 for males, or ≥ 104 for females, g/m(2)) or not (p=0.627). This study suggests that OPG is secreted into the coronary circulation and is associated with concentric remodeling/hypertrophy of LV, possibly in interactions with the renin-angiotensin system.

Raman-induced Kerr-effect dual-comb spectroscopy

We report on the first (to our knowledge) demonstration of nonlinear dual-frequency-comb spectroscopy. In multi-heterodyne femtosecond Raman-induced Kerr-effect spectroscopy, the Raman gain resulting from the coherent excitation of molecular vibrations by a spectrally narrow pump is imprinted onto the femtosecond laser frequency comb probe spectrum. The birefringence signal induced by the nonlinear interaction of these beams and the sample is heterodyned against a frequency comb local oscillator with a repetition frequency slightly different from that of the comb probe. Such time-domain interference provides multiplex access to the phase and amplitude Raman spectra over a broad spectral bandwidth within a short measurement time.

Comparison of the electrostatic binding sites on the surface of ferredoxin for two ferredoxin-dependent enzymes, ferredoxin-NADP(+) reductase and sulfite reductase

Plant-type ferredoxin (Fd), a [2Fe-2S] iron-sulfur protein, functions as an one-electron donor to Fd-NADP(+) reductase (FNR) or sulfite reductase (SiR), interacting electrostatically with them. In order to understand the protein-protein interaction between Fd and these two different enzymes, 10 acidic surface residues in maize Fd (isoform III), Asp-27, Glu-30, Asp-58, Asp-61, Asp-66/Asp-67, Glu-71/Glu-72, Asp-85, and Glu-93, were substituted with the corresponding amide residues by site-directed mutagenesis. The redox potentials of the mutated Fds were not markedly changed, except for E93Q, the redox potential of which was more positive by 67 mV than that of the wild type. Kinetic experiments showed that the mutations at Asp-66/Asp-67 and Glu-93 significantly affected electron transfer to the two enzymes. Interestingly, D66N/D67N was less efficient in the reaction with FNR than E93Q, whereas this relationship was reversed in the reaction with SiR. The static interaction of the mutant Fds with each the two enzymes was analyzed by gel filtration of a mixture of Fd and each enzyme, and by affinity chromatography on Fd-immobilized resins. The contributions of Asp-66/Asp-67 and Glu-93 were found to be most important for the binding to FNR and SiR, respectively, in accordance with the kinetic data. These results allowed us to map the acidic regions of Fd required for electron transfer and for binding to FNR and SiR and demonstrate that the interaction sites for the two enzymes are at least partly distinct.

Molecular cloning and sequencing of a cDNA encoding alanine-glyoxylate aminotransferase 2 from rat kidney

Alanine-glyoxylate aminotransferase (AGT) 2 is a pyridoxal 5'-phosphate dependent, mitochondrial enzyme which, in the rat, is expressed at a high level in the kidney. The amino acid sequences of nine tryptic and seven CNBr peptides of the rat kidney AGT2 were determined. Three overlapping cDNAs encoding the AGT2 were cloned on the basis of its partial amino acid sequences by means of a polymerase chain reaction-based approach involving rat kidney poly(A)+ RNA. The complete cDNA sequence comprised 1,919 bases, and contained a 1,536-base open reading frame which encodes a polypeptide of 512 amino acid residues with a putative presequence consisting of 39 amino acid residues at the amino terminus, giving a precursor protein with a molecular mass of 57,150 Da. The sequence of AGT2 exhibits significant homology with neither peroxisomal AGT1 from human liver nor mitochondrial AGT1 from rat liver. However, the sequence of AGT2 exhibited 30.8, 29.2, and 27.1% identity with those of Escherichia coli 4-aminobutyrate aminotransferase, rat ornithine aminotransferase, and Pseudomonas cepacia 2,2-dialkylglycine decarboxylase, respectively. The active site sequences were also well conserved among these aminotransferases. AGT2, thus, is more similar to the other aminotransferases than to AGT1. The results suggest that the rat kidney AGT2 may play a biological role in amino acid metabolism distinct from that of AGT1.

An open reading frame in the Rhodospirillum rubrum plasmid, pKY1, similar to algA, encoding the bifunctional enzyme phosphomannose isomerase-guanosine diphospho-D-mannose pyrophosphorylase (PMI-GMP)

The nucleotide sequence of a BglII fragment (3188 bp) from the plasmid pKY1 of Rhodospirillum rubrum was determined. A significant similarity was found between the amino acid sequences deduced from the nucleotide sequence of BglII fragment with that of algA, encoding the bifunctional enzyme with both the activities of phosphomannose isomerase and guanosine diphospho-D-mannose pyrophosphorylase of Pseudomonas aeruginosa.

Molecular organization of photochemical reaction complex in chromatophore membrane from Rhodospirillum rubrum as detected by immunochemical and proteolytic analyses

The molecular organization of photochemical reaction (PR) complex in chromatophores from Rhodospirillum rubrum was studied by a combination of proteolytic analysis with proteinase K followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunochemical analysis with rabbit polyclonal antibodies against its five subunits (H, M, L, alpha, and beta). The preparations used for comparison were reaction center complex (RC) (composed of H, M, and L), PR complex, and chromatophores (closed membranous vesicles of polar lipid bilayer having PR complex buried in the membrane). 1. RC was bound with anti-H, anti-M, and anti-L antibodies, whereas PR complex and chromatophores were bound with anti-H and anti-beta antibodies, but not with the other antibodies. 2. With PR complex, H (Mr 31,000 (31K)) was rapidly degraded into two peptides with Mr of 16K and 14.5K (abbreviated as 16K and 14.5K, respectively), M (27K) into 25.5K, and beta (11K) into 10K. Significantly later, the 25.5K of M was degraded into 24K, L (23K) into 19K, and alpha (12K) into 11K. With chromatophores, H and beta were degraded in a manner similar to that with PR complex, whereas M, L, and alpha were not degraded at all. With RC, H, M, and L were rapidly degraded. 3. With RC, the activity for photooxidation of P870 (photochemical activity) was hardly affected till H, M, and L had been degraded into less than 10K, 24K, and 19K, respectively. With PR complex, the absorbance spectrum due to the bacteriochlorophylls of light-harvesting complex-1 composed of alpha and beta (LH1-Bchl) changed in parallel to the degradation of alpha or 10K (a part of beta). 4. Together with the previous results (Ueda et al. (1985) J. Biochem. 98, 1487-1498), the present findings suggest that: 1) RC is directly surrounded by 12 alpha and further by 12 beta; 2) H and beta are mostly and partially exposed, respectively, on the outer surface of the membranous vesicle; 3) a small part of M is exposed on the inner surface of the membranous vesicle.

Effects of NaCl and glycerol on photosynthetic oxygen-evolving activity with thylakoid membranes from halophilic green alga Dunaliella tertiolecta

It is known that the halophilic green alga Dunaliella tertiolecta grows under hypertonic conditions (with NaCl), which induce the intracellular accumulation of high concentrations of glycerol in order to counterbalance the osmotic change. The effects of NaCl and glycerol on the photosynthetic oxygen-evolving activity of thylakoid membranes prepared from D. tertiolecta were investigated in relation to the dissociation of the membranes. It was found that proteins with Mr of 24,000, 17,000, and 13,000 were dissociated from thylakoid membranes of D. tertiolecta by washing with 1 M NaCl, whereas the photosynthetic oxygen-evolving activity was stimulated 2-fold by 0.1-1.5 M NaCl. The antibodies against spinach 24K and 17K proteins did not cross-react with Dunaliella 24K and 17K proteins, respectively. The salt-tolerant feature of the oxygen-evolving activity with Dunaliella thylakoid membranes may be related to the difference of the properties of these two proteins between D. tertiolecta and spinach. When the membranes were washed with 1 M Tris, proteins with Mr of 50,000 and 31,000 were also dissociated in addition to the 24K and 17K proteins described above. The antibody against spinach 33K protein cross-reacted with 31K protein of D. tertiolecta, showing that Dunaliella 31K protein corresponds to spinach 33K protein. When the membranes were treated with a mixture of 1% cholate and 2% deoxycholate, the oxygen-evolving activity was completely depressed, but the depressed activity was significantly restored by organic solvents. Glycerol and dimethylsulfoxide were the most effective for the restoration.(ABSTRACT TRUNCATED AT 250 WORDS)

Intermolecular relations of the photosystem II complex in spinach chloroplasts as detected by immunochemical assay

Polyclonal antibodies were prepared to the subunits of the spinach photosystem II fraction (PS II): p47, p43, p27, p33, p24, and p17. (The protein nomenclature refers to Mr). p47 and p43 are the subunits of reaction center complex, and p27 is light-harvesting chlorophyll protein. p33, p24, and p17 are extractable from PS II with 1 M Tris, and p24 and p17 with 1 M NaCl. With untreated PS II fractions, the antibody to p24 inhibited the photosynthetic oxygen-evolving activity, but not the DCPI-photoreduction activity in the presence of DPC, indicating that p24 played an important role in the former activity. Bindings of the respective antibodies to the PS II treated with sodium dodecyl sulfate were regarded as 100%. To untreated PS II, the bindings were 20-30% for p47, p43, and p27, about 50% for p33, and 70-80% for p24 and p17. To NaCl-washed PS II, the binding to p33 increased by 9%, indicating that p33 was adjacent or bound with p24 or/and p17. To Tris-washed PS II, the binding to p43 increased by 7%, indicating that p43 was adjacent or bound with p33. To PS II treated with 3% of Brij 58, only the binding to p27 increased appreciably. To PS II treated with 1% of octyl glucoside, the binding to p47 was still lower than 50%, whereas those to the other subunits were 74-91%. These values could be a measure of the extents to which the subunits were exposed to the aqueous phase, because of the nature of polyclonal antibodies. These results suggest that in intact PS II, p47, p43, and p27 were in most part buried in the inside, p47 being located at the most central and p27 at the outermost part, whereas p33, p24, and p17 were exposed to the outside by 50-75%.