To improve security and privacy, we are moving our web pages and services from HTTP to HTTPS. To give users of web services time to transition to HTTPS, we will support separate HTTP and HTTPS services until the end of 2017. From January 2018 most HTTP traffic will be automatically redirected to HTTPS. [more...] View this page in https
Proteins which transport small hydrophobic molecules such as steroids, bilins,
retinoids, and lipids share limited regions of sequence homology and a common
tertiary structure architecture [1,2,3,4,5]. This is an eight stranded
antiparallel β-barrel with a repeated + 1 topology enclosing a internal
ligand binding site [1,3]. The name 'lipocalin' has been proposed  for
this protein family. Proteins known to belong to this family are listed below
(references are only provided for recently determined sequences).
α-1-microglobulin (protein HC), which seems to bind porphyrin.
α-1-acid glycoprotein (orosomucoid), which can bind a remarkable array
of natural and synthetic compounds .
Aphrodisin which, in hamsters, functions as an aphrodisiac pheromone.
Apolipoprotein D, which probably binds heme-related compounds.
β-lactoglobulin, a milk protein whose physiological function appears to
Complement component C8 γ chain, which seems to bind retinol .
Crustacyanin , a protein from lobster carapace, which binds astaxanthin,
Epididymal-retinoic acid binding protein (E-RABP)  involved in sperm
Insectacyanin, a moth bilin-binding protein, and a related butterfly bilin-
binding protein (BBP).
Late Lactation protein (LALP), a milk protein from tammar wallaby .
The sequences of most members of the family, the core or kernal lipocalins,
are characterized by three short conserved stretches of residues [3,18].
Others, the outlier lipocalin group, share only one or two of these [3,18]. A
signature pattern was built around the first, common to all outlier and kernal
lipocalins, which occurs near the start of the first β-strand.
It is suggested, on the basis of similarities of structure, function,
and sequence, that this family forms an overall superfamily, called the
calycins, with the avidin/streptavidin <PDOC00499> and the cytosolic fatty-
acid binding proteins <PDOC00188> families [3,19].
PROSITE is copyright. It is produced by the SIB Swiss Institute
Bioinformatics. There are no restrictions on its use by non-profit
institutions as long as its content is in no way modified. Usage by and
for commercial entities requires a license agreement. For information
about the licensing scheme send an email to
or see: prosite_license.html.