Pathways & interactions
Sugar isomerase (SIS) (IPR001347)
Short name: SIS
Overlapping homologous superfamilies
- Sugar isomerase (SIS) (IPR001347)
- AgaS, SIS domain (IPR035464)
- Bifunctional phosphoglucose/phosphomannose isomerase, SIS domain 1 (IPR035484)
- Fructosamine deglycase FrlB, SIS domain 1 (IPR035488)
- GlmS/AgaS, SIS domain 1 (IPR035466)
- GlmS/FrlB, SIS domain 2 (IPR035490)
- KpsF-like, SIS domain (IPR035474)
- RpiR-like, SIS domain (IPR035472)
The sugar isomerase (SIS) domain is a phosphosugar-binding module that is found in a variety of eubacterial, archaebacterial and eukaryotic proteins that have a role in phosphosugar isomerization or regulation [PMID: 10203754]. In enzymes, the SIS domain can have a catalytic function as an isomerase and bind to phosphorylated sugars. In bacterial transcriptional regulators of the rpiR family, the domain seems to bind substrates implicated in the genes for sugar metabolism that are controlled by the regulator. The SIS domain is found in one or two copies and can be linked to additional domains, such as helix-turn-helix (HTH), CBS, glutamine amidotransferases type 2, or phosphopantetheine-attachment [PMID: 10203754, PMID: 18049859].
The SIS domain has an alpha-beta structure and is dominated by a five-stranded parallel beta sheet flanked on either side by alpha helices forming a three- layer alpha-beta-alpha sandwich [PMID: 9739095]. The fold shows similarities to that of glucose-6-phosphate isomerase.