A signal sequence mutant defective in export of ribose-binding protein and a corresponding pseudorevertant isolated without imposed selection.

Ribose-binding protein is exported to the periplasmic compartment of Escherichia coli by a process that involves proteolytic cleavage of an amino-terminal extension of amino acids from the precursor form of the protein. In a collection of mutants isolated as defective in the Rbs transport system, a strain was identified that contained only precursor ribose-binding protein, none of which was exported to its normal location in the periplasm. The mutated rbsB contained a base substitution that results in a change of leucine to a proline at position-17 in the signal sequence.

Fluorescent substrate analogue for adenosine deaminase: 3'-O-[5-(dimethylamino)naphthalene-1-sulfonyl]adenosine.

The synthesis of the fluorescent derivative of adenosine, by reaction with 5-(dimethylamino)naphthalene-1-sulfonyl chloride in dry pyridine at low temperature, yielding 3'-O-[5-(dimethylamino)naphthalene-1-sulfonyl]adenosine (3'-O-dansyladenosine), is here described. 3'-O-Dansyladenosine is partially soluble in water (approximately 10(-4) M) and upon excitation at 325 nm exhibits maximum fluorescence emission at 516 +/- 22 nm (corrected) in buffered aqueous solution at pH 7.6 with a quantum yield of 0.