Oligomeric Properties of Survival Motor Neuron·Gemin2 Complexes

Abstract

Background:The survival motor neuron (SMN) protein forms oligomeric complexes involved in ribonucleoprotein (RNP) biogenesis. Results: SMN forms stable dimers, which in turn self-associate to form tetramers and octamers. Conclusion: SMN complexes form discrete oligomers with unusually large hydrodynamic sizes. Significance: Understanding the oligomeric nature of SMN provides an important foundation for exploring the biochemical bases of RNP assembly and spinal muscular atrophy.

SMN - A chaperone for nuclear RNP social occasions?

“…In the fission yeast system, dimers and tetramers are the only species observed. 102 Human SMN-Gem2 forms dimers to octamers and possibly even larger complexes (Fig. 2B).…”

“…101,102 The core of this helical domain contains a highly conserved YxxxYxxxY motif. 101 Notably, phylogenetic analysis reveals that this motif can be extended on both ends to form a longer LxxxLxxxYxxxYxxxYxxxL helix (A.…”

“…66,114 As the concentration increases, this unit exists in an equilibrium mixture containing dimers, tetramers and octamers of SMN-Gem2. 102 Importantly, the SMNGem2 complex does not multimerize by forming symmetric bundles. 102 Instead, SMN tetramers are formed by a dimer of dimers (Fig.…”

“…102 Importantly, the SMNGem2 complex does not multimerize by forming symmetric bundles. 102 Instead, SMN tetramers are formed by a dimer of dimers (Fig. 2B).…”

“…Octamers appear to form via self-association of tetramers, although the existence of a hexameric SMN complex cannot be ruled out. 102 In vivo, human SMN-Gem2 cosediments with Gemins3-8, 115 however, the relative stoichiometries of these proteins are completely unknown.…”