ClpB in a cyanobacterium: predicted structure, phylogenetic relationships, and regulation by light and temperature.

The sequence of a genomic clone encoding a 100-kDa stress protein of Plectonema boryanum (p-ClpB) was determined. The predicted polypeptide contains two putative ATPase regions located within two highly conserved domains (N1 and N2), a spacer region that likely forms a coiled-coil domain, and a highly conserved consensus CK2 phosphorylation domain. The coiled-coil region and the putative site of phosphorylation are not unique to p-ClpB; they are present in all ClpB sequences examined and are absent from the ClpB paralogs ClpA, ClpC, ClpX, and ClpY. Small quantities of a 4.5-kb p-clpB transcript and 110-kDa cytosolic p-ClpB protein were detected in cells grown under optimal conditions; however, increases in the quantities of the transcript and protein were observed in cells grown under excess light and low temperature conditions. Finally, we analyzed ClpA, ClpB, and ClpC sequences from 27 organisms in order to predict phylogenetic relationships among the homologs. We have used this information, along with an identity alignment, to redefine the Clp subfamilies.

Kinesin light chain in a eubacterium.

A eubacterial homolog of a kinesin light chain gene has been isolated and characterized from the cyanobacterium Plectonema boryanum. Although the eubacterial and eukaryotic kinesin light chains are highly similar in amino acid sequence, the eubacterial sequence differs in several distinguishing structural features, including the absence of a putative PEST domain and the presence of additional highly conserved imperfect tandem repeats. Two soluble kinesin light chain antigens have been identified from whole-cell lysates by immunoblot analysis. Attempts to identify a canonical kinesin heavy-chain gene or protein were unsuccessful, suggesting that a kinesin heavy chain may be absent or unnecessary for kinesin light-chain function in this eubacterium. Our findings establish that certain basal elements of eukaryotic cellular transport appear to be resident in eubacteria. We discuss the possibility that the eukaryotic kinesin light chain was acquired by lateral gene transfer.

Mitigation of injury in canine lung grafts by exogenous surfactant therapy.

BACKGROUND: Exogenous surfactant therapy of lung donors improves the preservation of normal canine grafts. The current study was designed to determine whether exogenous surfactant can mitigate the damage in lung grafts induced by mechanical ventilation before procurement. METHODS AND RESULTS: Five donor dogs were subjected to 8 hours of mechanical ventilation (tidal volume 45 ml/kg). This produced a significant decrease in oxygen tension (p = 0.007) and significant increases in bronchoscopic lavage fluid neutrophil count (p = 0.05), protein concentration (p = 0.002), and the ratio of poorly functioning small surfactant aggregates to superiorly functioning large aggregates (p = 0.02). Five other animals given instilled bovine lipid extract surfactant and undergoing mechanical ventilation in the same manner demonstrated no significant change in oxygen tension values, lavage fluid protein concentration, or the ratio of small to large aggregates. All 10 lung grafts were then stored for 17 hours at 4 degrees C. Left lungs were transplanted and reperfused for 6 hours. After 6 hours of reperfusion the ratio of oxygen tension to inspired oxygen fraction was 307 +/- 63 mm Hg in lung grafts administered surfactant versus 73 +/- 14 mm Hg in untreated grafts (p = 0.007). Furthermore, peak inspired pressure was significantly (p < 0.05) lower in treated animals from 90 to 360 minutes of reperfusion. Analysis of lavage fluid of transplanted grafts after reperfusion revealed small to large aggregate ratios of 0.17 +/- 0.04 and 0.77 +/- 0.17 in treated versus untreated grafts, respectively (p = 0.009). CONCLUSIONS: Instillation of surfactant before mechanical ventilation reduced protein leak, maintained a low surfactant small to large aggregate ratio, and prevented a decrease of oxygen tension in donor animals. After transplantation, surfactant-treated grafts had superior oxygen tension values and a higher proportion of superiorly functioning surfactant aggregate forms in the air space than untreated grafts. Exogenous surfactant therapy can protect lung grafts from ventilation-induced injury and may offer a promising means to expand the donor pool.

Evaluation of surfactant treatment strategies after prolonged graft storage in lung transplantation.

We have previously documented alterations in endogenous surfactant after lung transplantation and improved graft function in some dogs after instillation of bovine lipid extract surfactant (bLES) into the recipient. To determine the effect of bLES delivery method and timing of treatment on physiologic response and surfactant recovery, 21 canine left lung grafts were divided into four groups: (1) Treatment of the donor for 3 h with aerosolized bLES prior to graft storage (Donor Aerosol); (2) Treatment of the recipient with instilled bLES immediately after transplantation (Recipient Instilled); (3) No bLES treatment (Control); and (4) Aerosolized bLES in donors and instilled bLES in recipients (Combined Therapy). Aerosolized bLES was labeled with [3H]-dipalmitoylphosphatidylcholine (DPPC) and instilled bLES with [14C]-DPPC. Grafts were stored for 36 h, transplanted and reperfused for 6 h. The native right and transplanted left lungs were then lavaged and protein yield, surfactant aggregates, and bLES recovery were measured. After 6 h of reperfusion, PO2/FlO2 ratio was significantly better after Combined Therapy (372 +/- 52 mm Hg) than in the Recipient Instilled (117 +/- 47 mm Hg) and Control groups (87 +/- 26 mm Hg), with intermediate values in Donor Aerosol dogs (232 +/- 64 mm Hg). The recovery of donor aerosolized bLES from transplanted lungs was increased in dogs given Combined Therapy versus Donor Aerosol treatment alone (p = 0.03). Furthermore, with Combined Therapy there was an increased percentage of instilled bLES recovered from transplanted lungs compared with the Recipient Instilled group. We conclude that surfactant treatment strategies influence physiologic response and bLES recovery after prolonged lung preservation. Treatment of lung donors with exogenous surfactant prior to graft storage was associated with less severe lung injury. Combined donor and recipient bLES therapy resulted in a superior physiologic response during reperfusion in this model.