Galactose binding lectin domain Galactose binding lectin domain In molecular biology, the galactose binding lectin domain is a protein domain. It is found in many proteins including the lectin purified from sea urchin ("Anthocidaris crassispina") eggs, SUEL. This lectin exists as a disulfide-linked homodimer of two subunits; the dimeric form is essential for hemagglutination activity. The sea urchin egg lectin (SUEL) forms a new class of lectins. Although SUEL was first isolated as a D-galactoside binding lectin, it was later shown that it binds to L-rhamnose preferentially. L-rhamnose and D-galactose share the same hydroxyl group orientation at C2 and C4 of the pyranose ring
Beta-keratin whose flight capabilities have been questioned, would have had avian, but not feather, β-keratins. The small alvarezsaurid dinosaur "Shuvuuia deserti" shows evidence of a featherlike skin covering. Analysis by Schweitzer "et al." (1999) showed that these featherlike structures consisted of beta-keratin. There are two main forms of keratin, alpha-keratin and beta-keratin. Alpha-keratin is seen in humans and other mammals, beta-keratin is present in birds and reptiles. Beta-keratin is harder than alpha-keratin. Structurally alpha-keratin have alpha-helical coiled coil structure while beta-keratin have twisted beta sheet structure.bIn the case of β-sheets, this allows sterically-unhindered hydrogen bonding between the amino and carboxyl groups