Table 1. 5 most commonly observed amino acids and ligands as acceptors or donors in protein–ligand SHBs.

SHB acceptor		SHB donor
Amino acid	Occurrence	Amino acid	Occurrence
Asp	407	Ser	211
Glu	319	Tyr	129
Thr	77	Thr	110
Ser	63	Lys	95
Tyr	46	His	95

SHB acceptor		SHB donor
Ligand	Occurrence	Ligand	Occurrence
FAD/FMN	51	NADP/NAD	96
Heme	45	α-l-Fucose	77
NADP/NAD	38	FAD/FMN	59
N-Acetyl-d-glucosamine	19	α-d-Mannose	40
α-l-Fucose	13	Heme	36