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- ***********************************
- * Glutamine synthetase signatures *
- ***********************************
-
- Glutamine synthetase (EC 6.3.1.2) (GS) [1] plays an essential role in the
- metabolism of nitrogen by catalyzing the condensation of glutamate and ammonia
- to form glutamine.
-
- There seem to be three different classes of GS [2,3,4]:
-
- - Class I enzymes (GSI) are specific to prokaryotes, and are oligomers of 12
- identical subunits. The activity of GSI-type enzyme is controlled by the
- adenylation of a tyrosine residue. The adenylated enzyme is inactive.
- - Class II enzymes (GSII) are found in eukaryotes and in bacteria belonging
- to the Rhizobiaceae, Frankiaceae, and Streptomycetaceae families (these
- bacteria have also a class-I GS). GSII are octamer of identical subunits.
- Plants have two or more isozymes of GSII, one of the isozymes is
- translocated into the chloroplast.
- - Class III enzymes (GSIII) has, currently, only been found in Bacteroides
- fragilis. It is a hexamer of identical chains. It is much larger (729 amino
- acids) then GSI (450 to 470 amino acids) or GSII (350 to 420 amino acids)
- enzymes.
-
- While the three classes of GS's are clearly structurally related, the sequence
- similarities are not so extensive. As signature patterns we selected three
- conserved regions. The first pattern is based on a conserved tetrapeptide in
- the N-terminal section of the enzyme, the second one is based on a glycine-
- rich region which is thought to be involved in ATP-binding. The third pattern
- is specific to class I glutamine synthetases and includes the tyrosine residue
- which is reversibly adenylated.
-
- -Consensus pattern: [FYW]-D-G-S-S
- -Sequences known to belong to this class detected by the pattern: ALL, except
- for GS-I and GS-III from Rhizobium leguminosarum, and GS from Sulfolobus
- solfataricus.
- -Other sequence(s) detected in SWISS-PROT: 14.
-
- -Consensus pattern: K-P-[LIVMFYA]-x(3,5)-[NP]-G-[GSTAN]-G-x-H-x(3)-S
- -Sequences known to belong to this class detected by the pattern: ALL, except
- for GS from C.elegans, mouse and GS-III from Rhizobium leguminosarum.
- -Other sequence(s) detected in SWISS-PROT: NONE.
-
- -Consensus pattern: K-[LIVM]-x(5)-[LIVMA]-D-[RK]-[DN]-[LI]-Y
- [Y is the site of adenylation]
- -Sequences known to belong to this class detected by the pattern: ALL class-I
- GS, except for Clostridium acetobutylicum.
- -Other sequence(s) detected in SWISS-PROT: NONE.
-
- -Expert(s) to contact by email: Tateno Y.
- ytateno@genes.nig.ac.jp
-
- -Last update: June 1994 / Patterns and text revised.
-
- [ 1] Eisenberg D., Almassy R.J., Janson C.A., Chapman M.S., Suh S.W.,
- Cascio D., Smith W.W.
- Cold Spring Harbor Symp. Quant. Biol. 52:483-490(1987).
- [ 2] Kumada Y., Benson D.R., Hillemann D., Hosted T.J., Rochefort D.A.,
- Thompson C.J., Wohlleben W., Tateno Y.
- Proc. Natl. Acad. Sci. U.S.A. 90:3009-3013(1993).
- [ 3] Shatters R.G., Kahn M.L.
- J. Mol. Evol. 29:422-428(1989).
- [ 4] Hill R.T., Parker J.R., Goodman H.J.K., Jones D.T., Woods D.T.
- J. Gen. Microbiol. 135:3271-3279(1989).
-