sentence: Thus , although a common transport function may be attributed to all VDAC isoforms , there appear to be unique physiological roles that are not well understood.When reconstituted into planar lipid membranes ( PLMs ) , VDAC1 and 2 form highly conductive weakly anionic-selective channels that facilitate the exchange of negatively charged respiratory substrates and adenine nucleotides ( Hodge and Colombini , 1997 ; Xu et al ., 1999 ; Colombini , 2004 ; Maurya and Mahalakshmi , 2015 ) .