SUMO protein

From Wikipedia, the free encyclopedia

Small Ubiquitin-related Modifier or SUMO proteins are a family of small proteins that are covalently attached to and detached from other proteins in cells to modify their function. SUMOylation is a post-translational modification involved in various cellular processes, such as nuclear-cytosolic transport, transcriptional regulation, apoptosis, protein stability, response to stress, and progression through the cell cycle.

SUMO proteins are similar to ubiquitin, and SUMOylation is directed by an enzymatic cascade analogous to that involved in ubiquitination. In contrast to ubiquitin, SUMO is not used to tag proteins for degradation. Mature SUMO is produced when the last four amino acids of the C-terminus have been cleaved off.

SUMO family members often have dissimilar names; the SUMO1 homologue in yeast, for example, is called SMT3 (suppressor of mif two 3). Several pseudogenes have been reported for this gene.

Structure schematic of human SUMO1 protein made with iMol and based on PDB file 1A5R, an NMR structure; the backbone of the protein is represented as a ribbon, highlighting secondary structure; N-terminus in blue, C-terminus in red

The same structure represented with atoms represented as spheres to show the shape of the protein; human SUMO1, PDB file 1A5R

[edit] Function

SUMO modification of proteins has many functions. Among the most frequent and best studied are protein stability, nuclear-cytosolic transport, transcriptional regulation (mostly transcriptional repression). Unlike ubiquitin modification which targets proteins for degradation, SUMOylation increases a protein's lifetime. It can also change a protein's location in the cell. For example, the Sumo modification of hNinein leads to its movement from the centrosome to the nucleus [1]. In most cases Sumo attachment to transcriptional regulators correlates with inhibition of transcription [2]. There are many more proposed functions. Refer to the GeneRIFs of the Sumo proteins, e.g. human SUMO1 [3], to find out more.

[edit] Structure

Sumo proteins are small proteins; most are around 100 amino acids in length and 12 kDa in mass. The exact length and mass varies between Sumo family members and depends on which organism the protein comes from. For example, human SUMO1, also shown in the figures, is 101 residues long and has a mass of 11.6 kDa. Its homologues in rat and mice are also 101 residues long, while the presumed relative in C. elegans has only 91 amino acids.

The structure of human SUMO1 is depicted on the right. It shows SUMO1 as a globular protein with both ends of the amino acid chain (shown in red and blue) sticking out of the protein's centre. The spherical core consists of an alpha helix and a beta sheet. The diagrams shown are based on an NMR analysis of the protein in solution.

[edit] External links

• SUMO1 homology group from HomoloGene
• human SUMO proteins on ExPASy: SUMO1 SUMO2 SUMO3 SUMO4
• UniProt entry for rat Sumo1
• SUMO conjugation sequence in the SCAN protein family (PubMed Bookshelf)

review on the topic

• connection between ubiquitin & SUMO modification, 2005
• effect of SUMO on transcription, 2005
• possible link between Sumo & diabetes, 2005

[4] Role of sumoylation in transcription, 2003]

• Mary Beth Mudgett's lab (plants & bacterial infection)
• Peter O'Hare's lab (Herpes virus)
• Mary Dasso's section on cell cylce control
• Mary Ann Handel's lab (meiosis, spermatogenesis)
• Nam-Hai Chua's lab (plants, protein modification)
• Frauke Melchior's personal page
• Stefan Jentsch's lab
• Bones lab (plant immunology) has a summary page on sumoylation