Peptide aptamers of LIM-only protein 2 (Lmo2) were previously used to 
successfully treat Lmo2-induced tumours in a mouse model of leukaemia. Here we 
show that the Lmo2 aptamer PA207, either as a free peptide or fused to 
thioredoxin Trx-PA207, causes purified Lmo2 to precipitate rather than binding 
to a defined surface on the protein. Stabilisation of Lmo2 through interaction 
with LIM domain binding protein 1 (Ldb1), a normal binding partner of Lmo2, 
abrogates this effect. The addition of free zinc causes Trx-PA207 to self 
associate, suggesting that PA207 destabilises Lmo2 by modulating normal 
zinc-coordination in the LIM domains. GST-pulldown experiments with other Lmo 
and Gata proteins indicates that PA207 can bind to a range of zinc finger 
proteins. Thus, PA207 and other cysteine-containing peptide aptamers for Lmo2 
may form a class of general zinc finger inhibitors.