HNRNPK belongs to the subfamily of ubiquitously expressed heterogeneous nuclear ribonucleoproteins (hnRNPs). The hnRNPs are RNA binding proteins and they complex with heterogeneous nuclear RNA (hnRNA). These proteins are associated with pre-mRNAs in the nucleus and appear to influence pre-mRNA processing and other aspects of mRNA metabolism and transport. While all of the hnRNPs are present in the nucleus, some seem to shuttle between the nucleus and the cytoplasm. The hnRNP proteins have distinct nucleic acid binding properties. HNRNPK is located in the nucleoplasm and has three repeats of KH domains that binds to RNAs. Recombinant human HNRNPK protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.