RCK (regulating the conductance of K+) domains are ubiquitous among a wide variety of cation translocation systems or channels. Whether it is inward or outward transport, RCK domains share high sequence similarity from protein to protein, suggesting that they perform important functions in these systems. Although specific functions are not yet fully understood, RCK domains bind nucleotides, a characteristic that has been suggested to be important for the open/closed transition. In some cases RCK domains can bind additional ligands, e.g. KefC binding to glutathione. This project provides an in-depth study of two equally important bacterial potassium uptake systems, Trk (from E. coli) and CglK (from C. glutamicum). In these systems, RCK domains form octamers that either are anchored (CglK) or are separate and bind to transmembrane partners (Trk). The overall objective of this study was to examine the ligand control of the Trk potassium uptake system, including ligand identification and binding effects on its conformation, and therefore activity control. A crystal structure of the Trk potassium uptake system from Vibrio parahaemolyticus, was published recently [1] and provided evidence of ADP/ATP switch as a control mechanism. In accordance with the aforementioned study, the work presented in this thesis provides strong evidence that both ADP and ATP can bind to E. coli TrkA. Furthermore, it was shown that NADH bind strongly to one of the two RCK domains present in TrkA protein. The data presented here suggest a more complex control mechanism of the E. coli Trk system. CglK is a major potassium uptake system of C. glutamicum, but little is known about its control mechanism. The mutagenesis approach was undertaken to learn more about the system and its underlying processes/mechanisms. The work shown in this thesis indicates a similarity of CglK to other potassium channels, such as MthK and GsuK. The functional mechanisms proposed for those two systems were proven to be similar to that of CglK, although the specific CglK activation ligands are still to be found.

No description available.

Thesis (Ph. D.)--University of Hong Kong, 1970. / Typewritten.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

No description available.

Not available / text

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. Description based on print version record. Includes bibliographical references.

The purposes of this research were to: (1) describe selected fluid and electrolyte changes that occur during the first four hours after open heart surgery; (2) determine whether significant hourly changes occurred in: blood pH, fluid intake, exogenous potassum chloride replacement, fluid output, or serum and urinary sodium and potassium levels; and finally, (3) delineate which of the above variables were most strongly related to changes in serum and urinary, sodium and potassium levels. Fifty-three patients who had undergone cardiac surgery involving cardiopulmonary bypass were studied. Urine and blood samples were collected every hour for the first four hours postoperatively and were analyzed for sodium and potassium content using flame photometry. Blood pH and exogenous potassium chloride replacement were recorded from the anesthesiologist's and nurse's records. Fluid intake and fluid output were measured directly by the investigator. Analyses included both descriptive and correlational statistics. In addition, a repeated measures procedure (MANOVA) was performed to discern performance trends over time. The data showed that hypokalemia (defined as a serum potassium level less than 4.0 mEq/L) was present in approximately 52 percent of the subjects for the first two postoperative hours and that by the fourth hour only 15 percent of the subjects were hypokalemic. In addition, subjects were noted to retain 2.47 liters of fluid over the four hour period. Significant differences in fluid output were noted across time. Serum sodium levels did not change significantly across time even though serum potassium levels did. The data indicated that the best predictors of hypokalemia were fluid intake and fluid output. Both of these variables had a significance level of p = .000. Regression analysis showed that fluid intake and exogenous potassium chloride replacement explained 11.9 percent of the variance in serum potassium at a significance level of p = .008. Furthermore, fluid output explained 7.3 percent of the variance in urinary potassium (p = .030).

A field study was conducted to assess phosphorus (P) and potassium (K) concentrations of both lactating and dry cow diets on Oregon's dairies. Thirty-seven dairy farms, located in western Oregon, were grouped according to geographic region, valley (V) or coast (C), and herd size, small (S) or large (L). Farms were visited on three separate occasions. During each visit, lactating and dry cow diets were recorded and corresponding feed ingredients were collected and analyzed for P and K. For each diet recorded, fecal and urine samples were collected and analyzed for P and K. When available, milk production data was obtained. During the initial visit, a survey was issued to producers to assess P and K knowledge as well as gather herd data and management information. Survey responses received indicated that two-thirds of participants were knowledgeable about P and its affects within the environment. Knowledge of K appeared to be less than that of P. Average P concentration of the lactating cow diet was 0.40% (DM basis) and did not differ between region (P=0.12) or herd size (P=0.76). Fecal P excretion did not differ between region (P=0.08) or herd size (P=0.27), however, a trend for larger fecal excretion in V farms contributed to the lower calculated apparent P digestibility for V than C. Potassium in lactating cow diet was greater (P=0.01) for C than V, however, but no difference between herd size (P=0.10) was determined. Overfeeding of K also occurred in dry cow diet with no difference between region (P=0.40) and herd size (P=0.72). Combining the fecal and urinary fractions, an individual lactating cow consuming 0.40% P (89.8 g) and 1.71% K (384.3 g) per day will excrete 24.0 kg of manure P and 76.3 kg of manure K annually. The magnitude of plant available P and K produced; requires Oregon producers to acquire additional land, an additional two-tenths ha/cow, to be to apply P and K at agronomic rates. / Graduation date: 2004