Lipocalin family

We have completed several structures each of NPl, NP2, and NP4 (31, 46 9, 110). These structures reveal the Rhodnius nitrophorins to have a fold dominated by an eight-stranded antiparallel beta-barrel, as shown in Fig. 15, and to rely on a remarkable ligand-induced conformational change for NO transport, described later. The structures confirm that the nitrophorins are completely unrelated to the globins, the only other heme-based gas transport proteins whose structures are known. Rather, their fold places them in the lipocalin family, for which several other examples are known (111-113). Our initial nitrophorin structure was of NPl and was determined using standard MIR and... 

Lipocalins are a family of proteins, which serve to transport small molecules around the body. A sub-set of the lipocalin family is found in the nasal mucosa and its members are known as odour-binding proteins (OBPs). These proteins are known to bind odorants but their role in olfaction is not understood at present. Each OBP is really a complex of two cup-shaped proteins with a hinge formed by the amino acid backbone of one passing through that of the other. Once they have bound a substrate, the cups come together at the rims and so form a spherical hydrophilic unit and an X-ray crystal structure of such an OBP odorant complex has been published (Bianchet et al., 1996). The role of the OBP could be to... 

Therefore, the model we described (see paragrapgh 9 of this chapter) using fluorescence spectroscopy showing the presence of a pocket in ap acid glycoprotein is in good agreement with that already described to other lipocalin family proteins. 

Figure 8.48. Three-dimensional stereo picture of O]- acid glycoprotein. The picture shows the +1 topology P-barrel that the protein has common with other members of the lipocalin family. Source Kopecky, V. Jr, Ettrich, R., Hofbauerova, K. and Baumruk. V, 2003, Biochemical Biophysical Research Communications. 300.41 >46.

Calycins, a protein superfamily comprising the fatty acid binding proteins (FABPs), streptavidin, a group of metalloproteinase inhibitors, lipocalin family, and triabin. 

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