Proteins lipocalins

Hiroaka, A. et al.. Charge microheterogeneity of the fi-trace proteins (lipocalin-type prostaglandin D synthase) in the cerebrospinal fluid of patients with neurological disorders analyzed by capillary isoelectric focusing. Electrophoresis, 22, 3433, 2001. 

Table 3.1 for the putative carriers in saliva, urine and nasal mucus the N-terminal sequences are highlighted against the pig salivary protein. All lipocalins or similar uncharacterised ( 20kDa) fractions with biological activity are extracellular, often found in quantity, 5 g/ml protein in male mouse urine and with a relatively high negative charge. 

The heterogeneity of the VN primary neurones is reflected in their modes of chemosensory preferences. The relative binding efficiencies for distinct odourant types onto the membrane sites is indeed functionally partitioned. When urinary fractions from male mice were applied to VN cells of females, stimulation by a lipophilic and volatile odourant fraction activated only the Gi protein-expressing cells. In contrast, Go activation was elicited by one of the lipocalin superfamily the MUP fraction containing an a-2-globulin (Krieger, 1999). This observation... 

Flower D.R. (1995). Multiple molecular recognition properties of the lipocalin protein family. J Mol Recog 8, 185-195. 

Flower D.R. (1996). The lipocalin protein family structure and function. Biochem J 318, 1-14. 

Miyawaki A., Matsushita F., Ryo Y. and Mikoshiba K. (1994). Possible pheromone-carrier function of 2 Lipocalin proteins in the vomeronasal organ. EMBO J 13, 5835-5842. 

Achen, M. G., et al. (1992). Protein synthesis at the blood-brain barrier. The major protein secreted by amphibian choroid plexus is a lipocalin. J. Biol. Chem. 267, 23170-4. 

Fujimori, K, et at (2005). Protein kinase C activates human lipocalin-type... 

Gerena, R. L., et at (1998). Identification of a fertility-associated protein in bull seminal plasma as lipocalin-type prostaglandin D synthase. Biol Reprod. 58, 826-33. 

Irikura, D., et at. (2007). Characterization of a major secretory protein in the cane toad (Bufo marinus) choroid plexus as an amphibian lipocalin-type prostaglandin D synthase. J. Biochem. 141, 173-80. 

Lepperdinger, G., el al. (1996). The lipocalin Xlcpll expressed in the neural plate of Xenopus laevis embryos is a secreted retinaldehyde binding protein. Protein Scl 5, 1250-60. 

The other major class of extracellular LBPs of mammals is the lipocalins (Flower, 1996). These are approximately 20 kDa, P-sheet-rich proteins, performing functions such as the transport of retinol in plasma or milk, the capture of odorants in olfaction, invertebrate coloration, dispersal of pheromones, and solubilizing the lipids in tears (Flower, 1996). The retinol-binding protein (RBP) of human plasma is found in association with a larger protein, transthyretin, the complex being larger than the kidney threshold and thus not excreted, although the RBP itself may dissociate from the complex to interact with cell surface receptors in the delivery of retinol (Papiz et al., 1986 Sundaram et al., 1998). 

Secondary structural predictions about NPAs, and direct biophysical measurements, have demonstrated that the NPAs are rich in a-helix, with no p-structure either predicted from secondary structure prediction algorithms, or detected by circular dichroism (Kennedy et al, 1995b). In this they are the antithesis of the similarly sized cLBPs and lipocalins. The predictions are that each individual NPA unit protein will fold into four main regions of helix, and it has been speculated that the tertiary structure is as a four-bundle helix protein, similar to other invertebrate carrier proteins (Sheriff et al., 1987). 

Lazar, J., Greenwood, D.R., Rasmussen, L.E.L. and Prestwich, G.D. (2002) Molecular and functional characterization of an odorant binding protein of the Asian elephant, Elephas maximas Implications for the role of lipocalins in mammalian olfaction. Biochemistry 41, 11786-11794. 

Within the limitations of sample size and extent of characterization, several general statements can be made in relation to the species described here, all of which express substantial concentrations of urinary lipocalins. First, these urinary proteins appear to be widespread across species that are not very closely related and occupy... 

Initially, it was suspected that the nitrophorins were insect hemoglobins. Indeed, they showed 45-48% homology with monomeric hemoglobins from insects, annelids, mollusks, nematodes, and even human 3 chains and leghemoglobin (44). However, in due time it became clear that these proteins were not globins at all, but rather, beta-barrel proteins called lipocalins (see Section III). As for the four nitrophorins, the sequences of NPl and NP4 are 90% identical, whereas those of NP2 and NP3 are 79% identical NPl and NP2, however, are only 38% identical. 

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... 

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