Carbohydrates attached to proteins and lipids characteristically displ
ay complex and heterogeneous structures. However, it is becoming incre
asingly clear that carbohydrates with definite biological functions al
so exhibit unique structural features. A number of glycoproteins and g
lycolipids have been shown to bear oligosaccharides containing sulfate
, Often, addition of a sulfate moiety turns a relatively common struct
ural motif into a unique carbohydrate with the potential to be recogni
zed by a specific receptor or lectin. This is clearly the case in thre
e systems in which sulfated oligosaccharides have been shown to play a
well-defined biological role: 1) control of the circulatory half-life
of luteinizing hormone, 2) symbiotic interactions be tween leguminous
plants and nitrogen-fixing bacteria, and 3) homing of lymphocytes to
lymph nodes. The rapidly growing list of glycoproteins and glycolipids
identified as bearing sulfated oligosaccharides suggests that sulfate
d carbohydrates play important biological roles in numerous other syst
ems as well.