spliceosome B complex (precatalytic spliceosome)

Function

• 3rd complex of spliceosome assembly
• the U4/U5/U6 tri-snRNP is recruited to the assembling spliceosome 'complex A' to form 'complex B' & following several rearrangements, 'Complex C' (the splicesome) is activated for catalysis

Structure

• consist of hnRNA, U1 snRNP, U2 snRNP, U4 snRNP, U5 snRNP, U6 snRNP, U2AF

Additional terms

• spliceosome