Localization of enzymes in Ureaplasma urealyticum (T-strain mycoplasma)

Abstract

Ureaplasma urealyticum cells were lysed by osmotic shock or by digitonin. The membrane fraction contained four to ten times as much protein as the cytoplasmic fraction. These values are in large excess of those reported for classical mycoplasmas, suggesting that the Ureaplasma membrane fraction was heavily contaminated with proteins derived from the growth medium. The U. urealyticum urease activity was localized in the cytoplasmic fraction, whereas the adenosine triphosphatase activity was localized in the membrane fraction. Significant urease activity could be detected also in nonviable cells. Urea, at concentrations above 0.25 M, was mycoplasmastatic to Acholeplasma laidlawii, Mycoplasma hominis, and U. urealyticum, so that the Ureaplasma urease did not afford preferential protection against urea toxicity. The intracellular localization of the urease would be expected to release ammonia from urea in the cytoplasm. The ammonia will take up protons to become ammonium ions. It can be hypothesized that the intracellular NH4+ plays a role in proton elimination or acid-base balance, which might be coupled to an energy producing ion gradient and/or transport mechanisms.

Microbial ureases: significance, regulation, and molecular characterization.

“…Jeffries (90,91) demonstrated that urease activity in 22 species of bacteria was associated with soluble extracts of the cells, which were ruptured by sonication or French pressure cell lysis. In cell fractionation studies of K. aerogenes (59), U. urea'lticiun (44,145,189,236), Providencia stiuar-tii (158), and Protelus lirilbilis (98), the majority of urease partitioned with the soluble cytoplasmic fraction. Analysis for control enzymes, known to reside in specific cell fractions, supported the conclusion that urease is cytoplasmic in these species.…”

“…Therefore, in this organism neither product of urea hydrolysis was used at significant levels by the cell. Masover et al (145) reasoned that ammonia generated by urease would be protonated at physiological pH, resulting in ammonium ion (NH4') formation. This T \N NH4 NH3 FIG.…”

“…Urease (protein 1) is a cytoplasmic protein; nevertheless, several membrane-bound proteins may be indirectly associated with urea degradation in certain microorganisms. For example, in U. ureal NWi-(cl/li urea hydrolysis was suggested to be coupled to ATP form-ation (145,190). In the proposed model, ureolysis genercates at net rise in intracellular pH and the resulting proton gradient is used to dIrive a proton-dependent ATP synthase (protein 2).…”

Ureaplasma urealyticum urease genes; use of a UGA tryptophan codon

“…U. ureaiyticum urease is localized in the cytoplasm of the celt (Masover et aL, 1977;Vinthier, 1976) and was shown to exhibit a specific activity greater than that of crystalline jack bean urease (Blanchard ef a/., 1988;Stemke et al, 1987). Three structural subunits of the purified enzyme were characterized as 72 kD, 14kD and 11 kD polypeptides (Thirkell etal.. 1989).…”

Ultrastructure of Ureaplasma urealyticum, serotype 8 and the use of immunogold to confirm the localisation of urease and other antigens

“…lost from cells as they age and lyse. It has been suggested that urease is cytosohc [6,12,13]. Sections probed with UU8/17 and pro-…”