The methodology of protein crystallography provides a number of potential 
bottlenecks. Here, an approach to successful structure solution of a difficult 
heterodimeric complex of two human proteins, paraspeckle component 1 (PSPC1) and 
non-POU domain-containing octamer-binding protein (NONO), that are involved in 
gene regulation and the structural integrity of nuclear bodies termed 
paraspeckles is described. With the aid of bioinformatic predictions and 
systematic screening of a panel of constructs, bottlenecks of protein 
solubility, crystallization, crystal quality and crystallographic pseudosymmetry 
were overcome in order to produce crystals that ultimately revealed the 
structure.