Detection of Two Membrane Polypeptides Induced by Abscisic Acid and Cold Acclimation: Possible Role in Freezing Tolerance

Membrane proteins labeled in vivo from cold-acclimated and ABA-treatedalfalfa seedlings of two cultivars differing in cold-tolerancehave been compared by SDS polyacrylamide gel electrophoresisand fluorography. Results thus obtained indicate that severalqualitative changes occur in the membrane protein-profile specificallyin response to cold acclimation or ABA treatment. While somepolypeptides disappear from the non-acclimated protein patterns,others specifically appear in response to acclimation. Separationby two-dimensional gel electrophoresis and fluorography hasconfirmed the above and has enabled us to detect two proteinsof Mr 42 kDa and 120 kDa that are induced by both acclimationand ABA treatment in the freezing tolerant cultivar. (Received November 30, 1987; Accepted February 22, 1988)     

Change of speciation of Cu(II) in growth medium due to uptake of ammonia byPseudomonas testosteroni during growth

Growth ofPseudomonas testosteroni in a medium containing 1mm Cu(II) causes a color change from blue to green. The spectrum of the supernatant solution from the blue culture shows an absorption at 660 nm, identical to that of 1mm [Cu(II)] in the medium. The green supernatant solution shows a UV absorption, which tails into the visible and so is responsible for the green color, and ad-d absorption at 720 nm. The absorption at 660 nm for the blue supernatant solution is probably due to [Cu(NH₃)₃(H₂O)₃]²⁺. Growth of the organism causes loss of ammonia and a speciation change to [Cu(NH₃)₂(H₂O)₄]²⁺, with a shift in absorption maximum from 660 to 720 nm. These conclusions are based upon the spectra of known aquaammine complexes of Cu(II) and calculations of the speciation of Cu(II) before and after growth. Change in metal speciation owing to nutrient uptake by an organism does not appear to have been recognized previously.     

Vacuolar H(+)-translocating pyrophosphatases: a new category of ion translocase.

The membrane surrounding the central vacuole of plant cells contains an H(+)-translocating ATPase (H(+)-ATPase) and an H(+)-translocating inorganic pyrophosphatase (H(+)-PPase). Both enzymes are abundant and ubiquitous in plants but the H(+)-PPase is unusual in its exclusive use of inorganic pyrophosphate (PPi) as an energy source. The lack of sequence identity between the vacuolar H(+)-PPase and any other characterized ion pump implies a different evolutionary origin for this translocase. The existence of the vacuolar H(+)-PPase, in conjunction with increasing recognition of PPi as a key metabolite in plant systems, necessitates reconsideration of ATP as the primary energy source for membrane transport in plant cells.     

Molecular characterization of the hemolysin determinant of Serratia marcescens.

The nucleotide sequence of a 7.3-kilobase-pair fragment of DNA encoding a hemolytic activity from Serratia marcescens was determined. Two large open reading frames were identified, designated shlA (Serratia hemolysin) and shlB, capable of encoding polypeptides of 165, 056 and 61,897 molecular weight, respectively. Both reading frames were expressed in vivo. The shlB gene product was localized to the outer membrane of Escherichia coli cells harboring the S. marcescens hemolysin determinant. Consistent with this location, a signallike sequence was identified at the N terminus of the polypeptide predicted from the nucleotide sequence of the shlB gene. Hyperexpression of the shlB locus permitted the identification of two shlB-encoded polypeptides of 65,000 and 62,000 molecular weight, respectively. Determination of the N-terminal amino acid sequence of the purified 62,000-molecular-weight protein confirmed that it was the mature form of the ShlB protein initially synthesized as a precursor (65,000-molecular-weight protein). By using polyclonal antisera raised against the purified proteins, ShlA and ShlB were identified in the outer membrane of S. marcescens. The shlA gene product was shown to interact with erythrocyte membranes, confirming it as the hemolysin proper. Both hemolysis and the interaction of ShlA with erythrocyte membranes did, however, require the ShlB function. Progressive deletion of the C terminus of the ShlA protein gradually reduced hemolytic activity until 37% of the amino acids had been removed. Elimination of 54% of the amino acids produced a nonhemolytic protein which, however, was still capable of associating with erythrocyte membranes.     

Motility response of Rhodobacter sphaeroides to chemotactic stimulation.

Tethered rotating cells of Rhodobacter sphaeroides varied widely in their stopping frequency; 45% of cells showed no stops of longer than 1 s, whereas others showed stops of up to several seconds. Individual cells alternated between stops and rotation at a fairly constant rate, without continuous variation. Addition of the chemoattractant propionate to free-swimming cells of R. sphaeroides increased the mean population swimming speed from 15 to 23 microns s-1. After correction for nonmotile cells, the percentage swimming at less than 5 microns s-1 dropped from approximately 22 to 8, whereas the percentage swimming at greater than 50 microns s-1 increased from 6 to 15. However, cells already swimming did not swim faster after propionate addition; the increase in the mean population speed after propionate addition was caused by an increase in the mean run length between stops from 25 to 101 microns. The increased run length was the result of a drop in both the stopping frequency and the length of a stop. Addition of propionate over the range of 10 microM to 1 mM decreased the stopping frequency; this decrease was almost entirely blocked by benzoate, a competitive inhibitor of propionate transport. The chemoattractants acetate and potassium had the same effect as propionate on the distribution of stopping frequency, which demonstrated that this is a general behavioral response to chemotactic stimulation. Adaptation to propionate stimulation was slow and very variable, cultures frequently showing little adaptation over 30 min. This characteristic may be the result of the lack of a highly specific chemosensory system in R. sphaeroides.     

Lactate and ventilatory thresholds: disparity in time course of adaptations to training

We tested the hypothesis that the lactate threshold (Tlac) during incremental exercise could be increased significantly during the first 3 wk of endurance training without any concomitant change in the ventilatory threshold (Tvent). Tvent is defined as O2 uptake (VO2) at which ventilatory equivalent for O2 [expired ventilation per VO2 (VE/VO2)] increased without a simultaneous increase in the ventilatory equivalent for CO2 (VE/VCO2). Weekly measurements of ventilatory gas exchange and blood lactate responses during incremental and steady-rate exercise were performed on six subjects (4 male; 2 female) who exercised 6 days/wk, 30 min/session at 70-80% of pretraining VO2max for 3 wk. Pretraining Tlac and Tvent were not significantly different. After 3 wk of training, significant increases (P less than 0.05) occurred for mean (+/- SE) VO2max (392 +/- 103 ml/min) and Tlac (482 +/- 135 ml/min). Tvent did not change during the 3 wk of training, despite significant (P less than 0.05) reductions in VE responses to both incremental and steady-rate exercise. Thus ventilatory adaptations to exercise during the first 3 wk of exercise training were not accompanied by a detectable alteration in the ventilatory "threshold" during a 1-min incremental exercise protocol. The mean absolute difference between pairs of Tlac and Tvent posttraining was 499 ml/min. Despite the significant training-induced dissociation between Tlac and Tvent a high correlation between the two parameters was obtained posttraining (r = 0.86, P less than 0.05). These results indicate a coincidental rather than causal relationship.(ABSTRACT TRUNCATED AT 250 WORDS)     

Morphology of the pericellular capsule in articular cartilage revealed by hyaluronidase digestion

To allow a more valid comparison between our previous ultrastructural data and the immunolocalization of type IX and other minor collagen species in cryosectioned cartilage, we examined both normal and testicular hyaluronidase-digested canine tibial cartilage by electron microscopy. Removal of matrix proteoglycans caused the pericellular capsule to collapse against the cell surface, suggesting that its normal anatomical position is mediated by pericellular matrix hydration. Detailed examination of the pericellular capsule and pericellular channel revealed fine, faintly banded fibrils and an amorphous component somewhat similar in structure to basement membrane collagens. Matrix vesicles and the electron-dense material of the interterritorial matrix were only partially digested by hyaluronidase. We propose that the pericellular capsule is composed of a "felt-like" network of minor collagen species which act synergistically to maintain both the composition of the pericellular matrix and the integrity of the chondrocyte/pericellular matrix complex during compressive loading.     

The engrailed locus of Drosophila: structural analysis of an embryonic transcript

cDNA clones originating from the engrailed gene of Drosophila have been isolated from recombinant phage libraries that were made using poly(A)+ RNA extracted from early embryos. The DNA sequence of one of these clones includes a homeo box, a 180 bp sequence present in several other Drosophila genes important in formation of body pattern during development. The homeo boxes found in the other Drosophila genes, as well as in cognate sequences from a wide range of segmented animals, including higher vertebrates, are highly conserved. By contrast, the homeo box within the engrailed gene diverges substantially and, unlike the other homeo boxes, is interrupted by an intervening sequence. The engrailed homeo box is located near the 3' end of a 1700 bp open reading frame. If translated, this sequence would produce a protein of unusual composition. We also show that a neighboring gene has a large region with strong homology to engrailed, and that it also contains a homeo box.     

Ta1, a novel 105 KD human T cell activation antigen defined by a monoclonal antibody

By using a murine monoclonal antibody produced against an IL 2-dependent human T cell line, we defined a T lineage-specific molecule, termed Ta1, that is expressed strongly on activated T lymphocytes of both the T4 and T8 subsets, as well as on T cell lines and clones, but only weakly on a fraction of resting T cells. SDS-PAGE analysis of immunoprecipitates from 125I-labeled, activated T cells demonstrates a single major band of apparent m.w. 105 KD under both reducing and nonreducing conditions. Unlike anti-IL 2 receptor antibodies, anti-Ta1 does not inhibit T cell proliferative responses to mitogen, antigen, or IL 2-containing medium. Moreover, anti-Ta1 has no effect on T cell-mediated cytotoxicity. Ta1 appears to be a novel human T cell-specific activation antigen that may serve as a useful marker of T cell activation in human disease.