Order of authorship in the original publication: Gellert, Mizuuchi, O'Dea, Nash. Discovery of DNA gyrase, the first type II topoisomerase to be discovered. 

"It is the only type II enzyme to retain its historical name. In contrast to other type II topoisomerases, DNA gyrase is the only enzyme that is capable of actively underwinding (i.e., negatively supercoiling) the double helix. It accomplishes underwinding by wrapping DNA around itself in a right-handed fashion (creating a positive supercoil) and carrying out its strand-passage reaction in a unidirectional manner (thus converting a positive to a negative supercoil). A motif in the C-terminal domain of the GyrA subunit, termed the GyrA box, is required for the enzyme to carry out this unique function.

"The ability of gyrase to wrap DNA during its strand passage reaction allows it to remove positive supercoils that accumulate in front of replication forks and transcription complexes even faster than it can introduce negative supercoils into relaxed DNA. Thus, DNA gyrase plays a critical role in opening the double helix for these two physiological processes. In addition, DNA gyrase works in conjunction with the ω protein (a type I topoisomerase that removes negative supercoils from the double helix), to maintain the global balance of DNA supercoiling in bacterial cells. Because of its DNA wrapping mechanism, DNA gyrase works primarily on DNA supercoiling; it is far less efficient at removing knots and tangles from the genome. In bacteria, these reactions are carried out primarily by the other type II topoisomerase, topoisomerase IV" (Encyclopedia of Biological Chemistry, [2004]).
Digital facsimile of the 1976 paper from PubMedCentral at this link.