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* Phosphatidylinositol 3- and 4-kinases signatures *
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Phosphatidylinositol 3-kinase  (PI3-kinase)  (EC 2.7.1.137)  [1] is  an enzyme
that phosphorylates  phosphoinositides on the 3-hydroxyl group of the inositol
ring. The  exact  function  of  the  three  products  of  PI3-kinase - PI-3-P,
PI-3,4-P(2) and PI-3,4,5-P(3) - is not yet known, although it is proposed that
they function  as second messengers in cell signalling. Currently, three forms
of PI3-kinase are known:

 - The  mammalian  enzyme  which is a heterodimer  of a 110 Kd catalytic chain
   (p110) and  an 85  Kd  subunit  (p85)  which allows it to bind to activated
   tyrosine protein kinases.
 - Yeast    TOR1/DRR1  and  TOR2/DRR2 [2], PI3-kinases required for cell cycle
   activation. Both are proteins of about 280 Kd.
 - Yeast VPS34 [3], a PI3-kinase involved in vacuolar sorting and segregation.
   VPS34 is a protein of about 100 Kd.

Phosphatidylinositol 4-kinase    (PI4-kinase)    (EC 2.7.1.-) [4] is an enzyme
that acts  on  phosphatidylinositol  (PI)  in  the  first commited step in the
production of  the  second  messenger inositol-1,4,5,-trisphosphate. Currently
a single form of PI4-kinase is known:

 - Yeast PIK1, a nuclear protein of 120 Kd.

The PI3- and PI4-kinases  share  a  well  conserved domain at their C-terminal
section; this domain  seems to be distantly related to the catalytic domain of
protein kinases  [2].  We  developed  two  signature  patterns  from  the best
conserved parts of this domain.

-Consensus pattern: [LIVMFA]-K-x(2)-[DE](2)-[LIVM]-R-Q-[DE]-x(3)-[LIVMFY]-Q
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: NONE.

-Consensus pattern: S-x-A-x(3)-[LIVM]-x(2)-[FY]-[LIVM](2)-x-[LIVM]-x-D-R-H-
                    x(2)-N
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: NONE.

-Last update: June 1994 / Patterns and text revised.

[ 1] Hiles I.D., Otsu M., Volinia S., Fry M.J., Gout I., Dhand R.,
     Panayotou G., Ruiz-Larrea F., Thompson A., Totty N.F., Hsuan J.J.,
     Courtneidge S.A., Parker P.J., Waterfield M.D.
     Cell 70:419-429(1992).
[ 2] Kunz J., Henriquez R., Schneider U., Deuter-Reinhard M., Movva N.,
     Hall M.N.
     Cell 73:585-596(1993).
[ 3] Schu P.V., Takegawa K., Fry M.J., Stack J.H., Waterfield M.D., Emr S.D.
     Science 260:88-91(1993).
[ 4] Garcia-Bustos J.F., Marini F., Stevenson I., Frei C., Hall M.N.
     EMBO J. 13:2352-2361(1994).