INTERACTION OF HUMAN PLASMA-MEMBRANE PROTEINS AND OLIGODEOXYNUCLEOTIDES

Two oligodeoxynucleotide (oligodN) binding proteins of 100-110 kDa on plasma membranes of human cell lines were recently identified by us. T hese two proteins seemed to play a role in oligodN uptake. In this stu dy, the impact of the chain length and the sequence of the oligodN on the interaction with those two proteins was investigated. Chain length of oligodN was an important determinant, but not the sole determinant for the interaction. Binding affinity of oligodNs was determined pred ominantly by base composition, where pyrimidine bases but not purine b ases were required in the sequence to retain high affinity. The bindin g kinetics of the homopolymers of deoxycytidine (dC(21)) and deoxythym idine (dT(21)) suggests that the proteins may have different binding s ites, with one site preferring thymine bases and the other cytosine ba ses. Moreover, some additional plasma membrane proteins were identifie d, with an apparent molecular mass ranging from 40 to 58 kDa, which co uld bind thymine bases but not cytosine bases. (C) 1998 Elsevier Scien ce Inc.