Protein which binds at least one S-adenosyl-L-methionine (SAM), or protein whose function is SAM-dependent. S-adenosyl-L-methionine, a conjugate of the nucleotide adenosine and the amino acid methionine, is a substrate/cofactor in numerous enzyme-catalyzed reactions. Enzymatic reactions that involve interactions of proteins with S-adenosyl-L-methionine include transfer of methyl, thiomethyl, aminoalkyl and adenosyl groups. It not only provides methyl groups to be transferred in numerous biological reactions, but also acts as a precursor in the biosynthesis of polyamines and metal ion chelating compounds. It is also a source of catalytic 5'-deoxyadenosyl radicals produced as reaction intermediates by a superfamily of radical enzymes. It is also involved in decarboxylation reactions.