Structure and sequence relationships in the lipocalins and related proteins.
The lipocalins and fatty acid-binding proteins (FABPs) are two recently identified protein families that both function by binding small hydrophobic molecules. We have sought to clarify relationships within and between these two groups through an analysis of both structure and sequence. Within a similar overall folding pattern, we find large parts of the lipocalin and FABP structures to be quantitatively equivalent. The three largest structurally conserved regions within the lipocalin common core correspond to characteristic sequence motifs that we have used to determine the constitution of this family using an iterative sequence analysis procedure. This afforded a new interpretation of the family, which highlighted the difficulties of determining a comprehensive and coherent classification of the lipocalins. The first of the three conserved sequence motifs is also common to the FABPs and corresponds to a conserved structural element characteristic of both families. Similarities of structure and sequence within the two families suggests that they form part of a larger "structural superfamily"; we have christened this overall group the calycins to reflect the cup-shaped structure of its members.
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Department of Physical Chemistry, R&D Labs, Loughborough, Leicestershire, United Kingdom.
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D000510:Alpha-Globulins / Q000737:chemistry / Q000145:classification; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry* / Q000145:classification*; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D006801:Humans; D019476:Insect Proteins; D007447:Invertebrate Hormones / Q000737:chemistry / Q000145:classification; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012177:Retinol-Binding Proteins / Q000737:chemistry / Q000145:classification; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid; D025521:Tumor Suppressor Proteins
D000510:Alpha-Globulins; D002352:Carrier Proteins; C107608:FABP7 protein, human; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D019476:Insect Proteins; D007447:Invertebrate Hormones; D009363:Neoplasm Proteins; D012177:Retinol-Binding Proteins; D025521:Tumor Suppressor Proteins; C043409:insecticyanin protein, insect