Mannan-binding lectin Mannan-binding lectin Mannose-binding lectin (MBL), also called mannose-binding protein or mannan-binding protein (MBP), is a lectin that is instrumental in innate immunity via the lectin pathway. MBL has an oligomeric structure (400-700 kDa), built of subunits that contain three presumably identical peptide chains of about 30 kDa each. Although MBL can form several oligomeric forms, there are indications that dimers and trimers are not biologically active and at least a tetramer form is needed for activation of complement. Human MBL2 gene is located on chromosome 10q11.2-q21. Mice have two homologous genes, but in human the first of them was lost.
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