Spliceosomal B complex
spliceosomal b complex
The spliceosomal B complex is an intermediate complex in the assembly of a spliceosome.    The <a href='/data/genegroup/#!/group/1504' target='_blank'>spliceosomal A complex</a> associates with the U4/U6.U5 tri-snRNP to generate the B complex. The B complex remains catalytically inactive until it undergoes extensive compositional and conformational rearrangements, including the dissociation of U1 and U4, resulting in the formation of the <a href='https://www.genenames.org/data/genegroup/#!/group/1508'>Bact complex</a>. This is converted into a catalytically active spliceosome (designated B*) by the action of the RNA helicase DHX16. The B* complex catalyses the first step of splicing, generating the cleaved 5' exon and intron-3' exon lariat intermediates and forming the <a href='https://www.genenames.org/data/genegroup/#!/group/1510'>C complex</a>.