Purification and biosynthesis of cottonseed (Gossypium hirsutum L.) catalase.

As part of our research on peroxisome biogenesis, catalase was purified from cotyledons of dark-grown cotton (Gossypium hirsutum L.) seedlings and monospecific antibodies were raised in rabbits. Purified catalase appeared as three distinct electrophoretic forms in non-denaturing gels and as a single protein band (with a subunit Mr of 57,000) on silver-stained SDS/polyacrylamide gels. Western blots of crude extracts and isolated peroxisomes from cotton revealed one immunoreactive polypeptide with the same Mr (57,000) as the purified enzyme, indicating that catalase did not undergo any detectable change in Mr during purification. Synthesis in vitro, directed by polyadenylated RNA isolated from either maturing seeds or cotyledons of dark-grown cotton seedlings, revealed a predominant immunoreactive translation product with a subunit Mr of 57,000 and an additional minor immunoreactive product with a subunit Mr of 64000. Labelling studies in vivo revealed newly synthesized monomers of both the 64000- and 57,000-Mr proteins present in the cytosol and incorporation of both proteins into the peroxisome without proteolytic processing. Within the peroxisome, the 57,000-Mr catalase was found as an 11S tetramer; whereas the 64,000-Mr protein was found as a relatively long-lived 20S aggregate (native Mr approx. 600,000-800,000). The results strongly indicate that the 64,000-Mr protein (catalase?) is not a precursor to the 57,000-Mr catalase and that cotton catalase is translated on cytosolic ribosomes without a cleavable transit or signal sequence.     

Adaptation of the bicinchoninic acid protein assay for use with microtiter plates and sucrose gradient fractions

The bincinchoninic acid protein assay has been adapted for use with microtiter plates and a plate reader to reduce the time needed for analyses. The total volume of the assay was reduced to 0.21 ml with various ratios of sample to reagent volume being used. The assay is sensitive to a limit of less than 1 microgram of bovine serum albumin. The assay is insensitive to the presence of the detergents sodium dodecyl sulfate, Triton X-100, and deoxycholate. In addition, the method has been adapted for determining the protein concentrations of sucrose density gradient fractions, which eliminates the need for removing the sucrose prior to assay.     

The retention and ultrastructural appearances of various extracellular matrix molecules incorporated into three-dimensional hydrated collagen lattices

Artificial extracellular matrices composed of collagen, glycosaminoglycans (GAG), proteoglycans (PG), plasma fibronectin (FN), and a hyaluronate-binding protein (HABP) have been prepared that morphologically resemble embryonic extracellular matrices in vivo at the light and electron microscope level. The effect of each of the above matrix molecules on the structure and "self-assembly" of these artificial matrices was delineated. (1) Matrix components assembled in vitro morphologically resemble their counterparts in vivo, for the most part. Scanning and transmission electron microscopy indicate that under our assembly and fixation conditions, collagen forms striated fibrils that are 125 nm in diameter, FN forms 30- to 60-nm granules, chondroitin sulfate proteoglycan (CSPG) forms 27- to 37-nm granules, chondroitin sulfate (CS) assembles into 100- to 250-nm spheres, and hyaluronate (HA) appears either as granular mats when fixed with cetylpyridinium chloride (CPC) or as 1.5- to 3-nm microfibrils when preserved with ruthenium red plus tannic acid. These molecules are known to assume the same configurations in embryonic matrices when the same preservation techniques are used with the exception of FN, which generally forms fibrillar arrays. (2) Addition of various matrix molecules can radically change the appearance of the collage gels. HA greatly expands the volume of the gel and increases the space between collagen fibrils. CSPG at low concentrations (less than 1 mg/ml) and CS at high concentrations (greater than 20 mg/ml) bundle the collagen fibrils into twisted ropes. (3) A variety of assays were used to examine binding between various matrix components and retention of these components in the hydrated collagen lattices. These assays included solid-phase binding assays, negative staining of spread mixtures of matrix components, cryostat sections of unfixed mixtures of matrix components, and retention of radiolabeled matrix molecules in fixed and washed gels. A number of these binding interactions may play a role in the assembly and stabilization of the matrix. (a) HA, CSPG, and FN bind to collagen. CS appears to only weakly bind to collagen, if at all. (b) FN promotes the increased retention of HA, CSPG, and to a very small degrees, CS, in collagen gels. Conversely, the GAG increase the retention of 3H-FN in the gels. Furthermore, FN binds to HA, CS, and CSPG as demonstrated by solid surface binding assays and morphological criteria. The increased retention of GAG and CSPG by the addition of FN may be due to both stabilization of binding to the collagen and trapping of matrix complexes within the gel. (c) HA binds to both CS and CSPG.(ABSTRACT TRUNCATED AT 400 WORDS)     

Ras-Transformed Cells Express Both CD44 and RHAMM Hyaluronan Receptors: Only RHAMM Is Essential for Hyaluronan-Promoted Locomotion

Hyaluronan (HA) is an important regulator of cell locomotion. We show that ras -transformed cells, termed 245 cells, respond to HA with an increase in random locomotion. We show that two HA receptors, RHAMM (receptor for hyaluronan-mediated motility) and CD44, are present on these ras -transformed fibroblasts. RHAMM is expressed as a 58-kDa protein and is distributed primarily as patches over lamellae. CD44 occurs largely as an 85- to 90-kDa protein that is distributed more or less evenly over the cell surface with small amounts concentrated at the tips of lamellae. CD44 and RHAMM both bind biotinylated HA in a transblot assay, indicating that they are both potential fibroblast HA receptors. CD44 binds approximately five times more HA than RHAMM as determined by densitometric analysis of transblots, indicating that this protein is the major HA receptor on fibroblasts. We assessed the role of these receptors in mediating the stimulatory effects of HA on cell motility by using antibody neutralization. Several antibodies to CD44 were used that inhibit HA/CD44 interactions. None of these had an effect on locomotory responses to HA, indicating that CD44 is not directly involved in mediating locomotion in response to HA on ras-transformed cells. In contrast, antibodies specific to RHAMM completely inhibited locomotion, indicating that RHAMM is the primary mediator of HA-promoted locomotion of ras -transformed cells.     

Hyaluronan and a cell-associated hyaluronan binding protein regulate the locomotion of ras-transformed cells

Hyaluronan (HA) and one of its cell binding sites, fibroblast hyaluronan binding protein (HABP), is shown to contribute to the regulation of 10T1/2 cell locomotion that contain an EJ-ras-metallothionein (MT-1) hybrid gene. Promotion of the ras-hybrid gene with zinc sulfate acutely stimulates, by 6-10-fold, cell locomotion. After 10 h, locomotion drops to two- to threefold above that of uninduced cells. Several observations indicate increased locomotion is partly regulated by HA. These include the ability of a peptide that specifically binds HA (HABR) to reduce locomotion, the ability of HA (0.001-0.1 micrograms/ml), added at 10-30 h after induction to stimulate locomotion back to the original, acute rate, and the ability of an mAb specific to a 56-kD fibroblast HABP to block locomotion. Further, both HA and HABP products are regulated by induction of the ras gene. The effect of exogenous HA is blocked by HABR, is dose-dependent and specific in that chondroitin sulfate or heparan have no significant effect. Stimulatory activity is retained by purified HA and lost upon digestion with Streptomyces hyaluronidase indicating that the activity of HA resides in its glycosaminoglycan chain. Uninduced cells are not affected by HA, HABR, or mAb and production of HA or HABP is not altered during the experimental period. These results suggest that ras-transformation activates an HA/HABP locomotory mechanism that forms part of an autocrine motility mechanism. Reliance of induced cells on HA/HABP for locomotion is transient and specific to the induced state.     

Characterization of a cDNA encoding cottonseed catalase

A 1.7 kb cDNA clone was isolated from our lambda gt11 library constructed from poly(A) RNA of 24-h-old cotyledons. The cDNA encodes a full-length catalase peptide (492 amino acid residues). The calculated molecular mass is 56,800, similar to that determined for purified enzyme (57,000 SDS-PAGE). Among higher plant catalases, this cotton catalase shows the highest amino acid sequence identity (85%) to the subunit of homotetrameric maize CAT 1, a developmental counterpart to the homotetrameric CAT A isoform of cotton seeds. Comparison of sequences from cotton, sweet potato, maize CAT 1, and yeast with bovine catalase revealed that the amino acid residues and regions that are involved in catalytic activity and/or required to maintain basic catalase structure, are highly conserved. The C-terminus region, which has the lowest nucleotide sequence identity between plant and mammalian catalases, does not terminate with a tripeptide, S-K/R/H-L, a putative targeting signal for peroxisomal proteins.     

Correlation of low and high density lipoprotein binding in vivo with rates of lipoprotein degradation in the rat. A comparison of lipoproteins of rat and human origin

These studies were done in the rat to correlate the ability of low and high density lipoproteins of rat (rLDL and rHDL) and human (hLDL and hHDL) origin to bind in vivo to specific tissues with the rates at which these same lipoprotein fractions were cleared from the circulation. The adrenal gland and liver manifested the greatest amounts of rLDL binding in vivo, but activity also was found in spleen, lung, kidney, ovary, and intestine. In contrast, little or no such binding was found utilizing either methyl-rLDL or hLDL. rHDL containing E apoprotein bound to the same group of tissues although in lesser amounts, except in the case of ovary and adrenal gland which bound disproportionately greater amounts of rHDL than rLDL. In keeping with these marked differences in tissue binding, the clearance of rLDL from the plasma equaled 847 +/- 36 microliters/h/100 g of rat while that of methyl-rLDL and hLDL was only 368 +/- 8 and 363 +/- 11 microliters/h/100 g of rat, respectively. When the steady state plasma level of rLDL was raised 2.5-fold, the clearance decreased slightly to 705 +/- 20 microliters/h/100 g of rat. The clearance of hLDL remained constant, however, at about 350 microliters/h/100 g of rat even when the plasma hLDL level was raised to very high values. The clearance of rHDL and hHDL equaled 644 +/- 16 and 408 +/- 13 microliters/h/100 g of rat, respectively, reflecting the more similar rate of binding of rHDL and hHDL to the tissues of the rat. Rates of whole animal sterol synthesis were lowered from 28 mumol/h to 8.8 mumol/h or 13 mumol/h by fasting and cholesterol feeding, respectively, and stimulated to 71 mumol/h by cholestyramine treatment. Under these same conditions, hepatic cholesterol synthesis could be lowered from the normal rate of 15 mumol/h to 4.2 mumol/h and raised to 50 mumol/h. None of these treatments, however, affected the plasma clearance of rLDL and rHDL. In contrast, treatment with ethinyl estradiol increased by 3-fold both the hepatic binding and the whole animal plasma clearance of rLDL. Following resection of approximately two-thirds of the liver under carefully controlled metabolic conditions, there was no change in the rate of hepatic cholesterol synthesis or rLDL binding in the remaining liver, but the clearance of chylomicrons, rLDL, and rHDL diminished by 67%, 26%, and 17%, respectively, suggesting that in the rat the liver was responsible for the degradation of approximately 97%, 39%, and 27%, respectively, of these lipoprotein fractions.     

Selective inhibition of prostaglandin biosynthesis by gold salts and phenylbutazone

Gold salts and phenylbutazone selectively inhibit the synthesis of PGF_2α and PGE₂ respectively. Lowered production of one prostaglandin species is accompanied by an increased production of the other. Selective inhibition by these drugs was observed in the presence of adrenaline, reduced glutathione and copper sulphate under conditions when most anti-inflammatory compounds inhibited PGE₂ and PGF_2α syntheses equally. It is postulated that selective inhibitors may have a different mode of action and beneficial effects may be related to the endogenous ratio of PGE to PGF required for normal function.     

Evaluation of a fine sediment biomonitoring tool across a wide range of temperate rivers and streams

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