Treatment of stiff-man syndrome with intravenous immunoglobulin.

Stiff-man syndrome (SMS) is a rare disorder characterized by progressive rigidity, stiffness, and spasms of axial and extremity muscles. The etiology of SMS is unknown, but evidence suggests a possible autoimmune basis. The recent successful use of intravenous immunoglobulin (IVIG) in treating various autoimmune neuromuscular disorders led us to try IVIG in an uncontrolled pilot study on three patients. All three showed subjective and objective improvement.

Active site of the enzyme which demethylates receptors during bacterial chemotaxis.

The CheB methylesterase catalyzes the hydrolysis of glutamyl methyl esters in bacterial chemoreceptor proteins. Studies with residue-specific inhibitors suggest that a cysteine residue is required. The nucleotide sequence of the cheB gene predicts a 349-amino acid protein with cysteine residues at positions 207 and 309. Oligonucleotide-directed mutagenesis was used to change each cysteine to an alanine. Whereas the Cys207-Ala mutation had essentially no effect on esterase activity, the Cys309-Ala mutation caused a complete inactivation of the enzyme. Cys309 is located adjacent to a sequence of amino acids which is characteristic of the beta-alpha-beta motif found in a number of nucleotide binding proteins associated with receptor function in vertebrate tissues. A central feature of this structure is Gly-X-Gly-X-X-Gly. Mutation of the second glycine in this region (Gly284) to a valine also caused a complete loss of esterase activity.