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Observations on membranes of Mycoplasma laidlawii strain B
Abstract:
The cytoplasmic membrane of Mycoplasma laidlawii strain B is solubilized by anionic and nonionic detergents, succinylation, phospholipase A, alkaline phosphatase, trypsin, and chymotrypsin. Cationic detergents are without effect, as are chelating agents, even in the presence of high concentrations of monovalent cation. The detergent-solubilized membrane exhibits one peak in the analytical ultracentrifuge, but the sedimentation coefficient is dependent upon concentration of detergent. Simple dialysis does not remove all of the sodium dodecylsulfate except from lipid-depleted membrane particles. Membranes bind sodium dodecylsulfate but acetone powders of membranes do not. Sulfated alcohols with chain lengths of C(14) and C(16) are more tightly bound than dodecylsulfate. A constant amount of di- and trivalent cation is bound by the membrane upon aggregation. Only a portion of this cation is removable with chelating agents. No chelating agent is bound by these aggregates. A portion of the lipid-depleted membrane particles is solubilized by negatively charged lipids and detergents, giving rise to aggregates in the presence of divalent cation. Fractionations of detergent-solubilized membranes by preparative gel electrophoresis and ammonium sulfate were inconclusive. Density gradient centrifugation of succinylated membranes yielded at least five fractions which exhibited homogeneity by ultracentrifugation. Analytical gel electrophoresis of these fractions demonstrated heterogeneity. The composition of these five fractions suggested separation of protein from lipid.
Insights
Mycoplasma laidlawii membranes solubilize with various treatments, but cationic detergents are ineffective. Density gradient centrifugation separated succinylated membranes into fractions, suggesting protein and lipid separation.
Area of Science:
- Cellular Biology
- Biochemistry
- Membrane Biophysics
Background:
- The cytoplasmic membrane of Mycoplasma laidlawii strain B is a complex structure.
- Understanding its composition and behavior under different treatments is crucial for cellular biology.
Purpose of the Study:
- To investigate the solubilization and fractionation of the Mycoplasma laidlawii cytoplasmic membrane.
- To determine the effects of various detergents and enzymatic treatments on membrane structure.
Main Methods:
- Solubilization using anionic and nonionic detergents, succinylation, and enzymatic treatments (phospholipase A, alkaline phosphatase, trypsin, chymotrypsin).
- Analytical ultracentrifugation to analyze detergent-solubilized membranes.
- Density gradient centrifugation of succinylated membranes.
- Gel electrophoresis for fraction analysis.
Main Results:
- Anionic and nonionic detergents, succinylation, and specific enzymes effectively solubilized the membrane, while cationic detergents and chelating agents did not.
- Detergent-solubilized membranes showed concentration-dependent sedimentation.
- Density gradient centrifugation of succinylated membranes yielded distinct fractions, indicating potential separation of membrane components.
- Analytical gel electrophoresis revealed heterogeneity within these fractions, suggesting a partial separation of protein and lipid.
Conclusions:
- The Mycoplasma laidlawii membrane can be effectively solubilized by a range of agents, with differential effects observed based on charge and type.
- Density gradient centrifugation offers a promising method for fractionating membrane components, potentially separating proteins from lipids.