{PDOC00193}
{PS00221; MIP}
{BEGIN}
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* MIP family signature *
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Recently the sequence  of a number of  different proteins, that all seem to be
transmembrane channel proteins, has been found to be  highly related [1 to 4].
These proteins are listed below.

 - Mammalian major intrinsic protein (MIP). MIP is the major component of lens
   fiber gap junctions.  Gap junctions  mediate  direct  exchange  of ions and
   small molecule from one cell to another.
 - Mammalian  aquaporins  [5].  These  proteins  form  water-specific channels
   that provide the  plasma  membranes  of  red  cells and kidney proximal and
   collecting tubules  with  high  permeability  to  water, thereby permitting
   water to move in the direction of an osmotic gradient.
 - Soybean nodulin-26, a major component of the peribacteroid membrane induced
   during nodulation in legume roots after Rhizobium infection.
 - Plants tonoplast intrinsic proteins (TIP). There  are  various  isoforms of
   TIP: alpha (seed), gamma, Rt (root), and Wsi (water-stress induced).  These
   proteins may allow the diffusion of water, amino acids and/or peptides from
   the tonoplast interior to the cytoplasm.
 - Bacterial glycerol facilitator protein (gene glpF), which  facilitates  the
   movement of glycerol across the cytoplasmic membrane.
 - Salmonella typhimurium propanediol diffusion facilitator (gene pduF).
 - Yeast FPS1, a glycerol uptake/efflux facilitator protein.
 - Drosophila neurogenic protein  'big brain' (bib).  This protein may mediate
   intercellular communication; it  may functions by allowing the transport of
   certain molecules(s) and thereby sending a signal for an  exodermal cell to
   become an epidermoblast instead of a neuroblast.
 - Yeast hypothetical protein YFL054c.
 - A hypothetical protein from the pepX region of lactococcus lactis.

The MIP family proteins seem to  contain six transmembrane segments.  Computer
analysis shows that these  protein  probably  arose  by  a  tandem, intragenic
duplication event from an ancestral protein that contained three transmembrane
segments.  As a signature pattern we selected a well conserved region which is
located  in  a  probable  cytoplasmic  loop   between   the second  and  third
transmembrane regions.

-Consensus pattern: [HNQA]-{D}-N-P-[STA]-[LIVMF]-[ST]-[LIVMF]-[GSTAFY]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: 5.

-Last update: December 2004 / Pattern and text revised.

[ 1] Reizer J., Reizer A., Saier M.H. Jr.
     CRC Crit. Rev. Biochem. 28:235-257(1993).
[ 2] Baker M.E., Saier M.H. Jr.
     "A common ancestor for bovine lens fiber major intrinsic protein,
     soybean nodulin-26 protein, and E. coli glycerol facilitator."
     Cell 60:185-186(1990).
     PubMed=2404610
[ 3] Pao G.M., Wu L.-F., Johnson K.D., Hofte H., Chrispeels M.J., Sweet G.,
     Sandal N.N., Saier M.H. Jr.
     "Evolution of the MIP family of integral membrane transport
     proteins."
     Mol. Microbiol. 5:33-37(1991).
     PubMed=2014003
[ 4] Wistow G.J., Pisano M.M., Chepelinsky A.B.
     "Tandem sequence repeats in transmembrane channel proteins."
     Trends Biochem. Sci. 16:170-171(1991).
     PubMed=1715617
[ 5] Chrispeels M.J., Agre P.
     "Aquaporins: water channel proteins of plant and animal cells."
     Trends Biochem. Sci. 19:421-425(1994).
     PubMed=7529436

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