Glutamic Acid (GLU OR E), usually known as glutamate in Foldit, is a hydrophilic amino acid. Its shape in Foldit is almost the same as glutamine, to which it is closely related. The CPK or EnzDes coloring options (found in view options) can be used to tell the two apart.
Glutamate's sidechain contains two oxygen atoms which can act as hydrogen bond acceptors. The end of the sidechain is a carboxyl group, the same structure found in the backbone of amino acids. The carboxyl group means glutamate's sidechain is formally considered acidic. See the Sidechain Bonding Gallery and the Sidechain Bonding Table for other sidechain donors and acceptors.
For more, see Glutamic acid on wikipedia.