ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The permeability of bacteriophage T4 and the change in T4 permeability caused by mutation to osmotic shock resistance are investigated here by quantification of the kinetics with which both a DNA-specific probe (ethidium) and a protein-specific probe [1,1′-bi(4-anilino) naphthalene-5,5′-di-sulfonic acid, or bis-ANS] bind to T4. In the case of an osmotic shock-resistant mutant, T40s41, both ethidium and bis-ANS bind with first order kinetics. The first-order rate constant (k*) for both bis-ANS and ethidium is a function of anion type and concentration. Adenosine triphosphate, phosphate, bisulfite, sulfate, and acetate anions all reduce k* below the k* observed when chloride is the only anion. When chloride is the only anion at 25°C, k* values for binding to T40s41 are orders of magnitude above k* values for binding to wild-type T4 (T4wt). At 25°C, k* forT4wt is too small to measure, but k* for T4wt increases at 50-55°C to values approaching those measured for T40s41, without inactivating T4wt, when chloride is the only anion; during heating, T4wt is stabilized by both ethidium and bis-ANS. Binding to T4wt is reversible at 50-55°C, but not at 25°C. Equilibrium binding of bis-ANS to T40s41 reveals 112 ± 24 sites per T4 capsid. Equilibrium binding of ethidium to T40s41 reveals both high- and low-affinity sites previously observed in the packaged DNA of other bacteriophages. The ATP-induced decrease in k* is not accompanied by a decrease in equilibrium binding. The following hypotheses are presented to explain the above data: (a) All detected bis-ANS binding sites on T4 are interior to the outer surface of T4. (b) The value of k* for both bis-ANS and ethidium is controlled at the port(s) of passage through the outer shell of the T4 capsid. (c) The anions present control k* values at the port(s) of entry, probably by controlling the size of this port. The effects on k* of phosphate explain the otherwise paradoxical observation [P. J. McCall and V. A. Bloomfield (1976) Biopolymers 15, 2323-2336] that in a phosphate buffer the permeabilities of T4wt and T40s41 are the same.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.360310103
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