Abstract: Mutant proteins of human DNA topoisomerase I having an amino acid sequence in which tyrosine at the 592nd position of human DNA topoisomerase I is lacking or replaced with phenylalanine and which contains at least 30 amino acids in succession of the amino acid sequence subsequent to the 542nd amino acid of human DNA topoisomerase I.Above described mutant proteins react with anti-Scl-70, antibody in the sera of autoimmune disease patients of diffuse scleroderma and can be produced by genetic engineering using E. coli, and therefore they are useful as a diagnostic agent of scleroderma.

Abstract: A torque limiter having an inner cylinder, an outer cylinder rotatably mounted around the inner cylinder, a closure member mounted between the outer cylinder and the inner cylinder to close one end of the outer cylinder, a coil spring mounted between the inner cylinder and the outer cylinder and having one end coupled to the outer cylinder and the other end coupled to the closure member so as to be tightened against the outer peripheral surface of the inner cylinder. The outer peripheral surface of the inner cylinder has a roughness Ra (arithmetical mean deviation) of 0.6-1.0, and the coil spring is formed of a wire having a circular cross-section.