All of the following are conjugated proteins EXCEPT

Proteins are broadly classified into simple, conjugated, and derived proteins based on their structural composition and the products of their hydrolysis.

Simple proteins are composed entirely of amino acids and yield only amino acids upon complete hydrolysis. Histones are a well-known example of simple proteins; they are highly basic proteins rich in arginine and lysine residues that associate with DNA in eukaryotic chromatin.

Conjugated proteins contain a protein part combined with a non-protein component called a prosthetic group. Haemoglobin is a conjugated protein (specifically a chromoprotein or metalloprotein) that contains a protein globin bound to an iron-containing heme group. Mucin is also a conjugated protein (specifically a glycoprotein) where carbohydrate chains are covalently linked to the protein backbone. Heparin is a glycosaminoglycan that exists biologically attached to a core protein to form a proteoglycan, which is classified as a conjugated protein structure.

Since histones are classified strictly as simple proteins and do not contain any non-protein prosthetic group, they are not conjugated proteins.

Answer: Histones