The lipocalin protein family: structure and function

Abstract

The lipocalin protein family is a large group of small extracellular proteins. The family demonstrates great diversity at the sequence level ; however, most lipocalins share three characteristic conserved sequence motifs, the kernel lipocalins, while a group of more divergent family members, the outlier lipocalins, share only one. Belying this sequence dissimilarity, lipocalin crystal structures are highly conserved and comprise a single eight-stranded continuously hydrogen-bonded antiparallel β-barrel, which encloses an internal ligand-binding site. Together with two other families of ligand-binding proteins, the fatty-acid-binding proteins (FABPs) and the avidins, the lipocalins form part of an overall structural superfamily : the calycins. Members of the lipocalin family are characterized by several common molecular-

Molecular and structural analyses of a novel temperature stress‐induced lipocalin from wheat and Arabidopsis

“…Sequence analysis revealed that the N-terminal portion of both wheat and Arabidopsis proteins possesses the three lipocalin SCRs. The SCR 1 region is located within aa 15^31 (GLDVARYMGRWYEIASF) in TaTIL and within aa 12^28 (GLNVERYMGRWYEIASF) in AtTIL and possesses the two conserved amino acids G and W [1,9] (Fig. 1).…”

“…The 28S ribosomal band stained with ethidium bromide is included to show RNA loads (7.5 Wg). NA7, NA12, non-acclimated plants grown for 7 and 12 days; CA1, CA6, CA36, cold-acclimated plants for 1,6 and 36 days; DA1 and DA5, coldacclimated plants (36 days) were deacclimated for 1 and 5 days; NaCl, plants treated with 300 mM NaCl for 18 h; ABA, plants treated with 0.1 mM ABA (Sigma) for 18 h; WS, water-stressed plants with a relative water content of 57% and 44%; HS, plants exposed to 40 ‡C for 1 h and 3 h (heat-shock); W, wounding stress for 3 h. Leaf, crown and roots of non-acclimated plants (NA7) and 6 days cold-acclimated (CA6). ARA, Arabidopsis plants; NA, nonacclimated plants; CA1, cold-acclimated for 1 day; HS 1 h, exposed to 45 ‡C for 1 h (heat-shock).…”

“…The list of potential ligands is constantly growing and includes diverse molecules such as steroids, pheromones, and odorant molecules. Lipocalins were early established as transport proteins, but it is becoming increasingly clear that some of them may be implicated in many other important functions such as modulation of cell growth and metabolism, binding of cellsurface receptors, nerve growth and regeneration, regulation of the immune response, smell reception, cryptic coloration, membrane biogenesis and repair, and induction of apoptosis [1]. In plants, only one study reported the presence of two lipocalin-like proteins.…”

Seasonal phenotype‐specific transcriptional reprogramming during metamorphosis in the European map butterfly Araschnia levana

“…2010). The LD prepupae also preferentially expressed at least one member of the lipocalin family of transporters, which carry small hydrophobic molecules such as steroids and lipids, and may play a role in insect coloration, immunity, olfaction and pheromone transport (Flower 1996). We also found that LD prepupae expressed higher levels of prophenoloxidase‐activating factor, which presumably activates the prophenoloxidase required for melanin formation in the darker summer phenotype.…”

Nanobodies: Chemical Functionalization Strategies and Intracellular Applications

“…Mutagenesis of the binding area resulted in a number of efficient affibodies that bind targets like human insulin or the cytokine TNFα 39. Anticalins are derived from the ß‐barrel‐structured lipocalins, a diverse class of proteins responsible for the transport, storage, synthesis, and sequestration of small hydrophobic molecules 40. Lipocalin‐based libraries have enabled the selection of anticalins against various targets with up to picomolar affinities 34.…”