Illustration of a leghaemoglobin molecule represented as a hamburger. Leghaemoglobin is a protein capable of binding molecular oxygen. It is similar to mitochondrial haemoglobin with a single haem group where oxygen molecules bind to the iron centre of haem. Leghaemoglobin is found in the nitrogen-fixing root nodules of leguminous plants. It is produced by legumes in response to the roots being colonised by nitrogen-fixing bacteria. Leghaemoglobin has been used in plant-based burgers to give a meat-like 'bloody' burger.