A protein containing more than one iron and acid-labile sulfur
displays electron-transfer activity but not classical enzyme function.
PAC, 1997, 69, 1251
(Glossary of terms used in bioinorganic chemistry (IUPAC Recommendations 1997))
on page 1275
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook