The results presented here are partially in contrast with the recent study of rSCL. Instead of seeing an unproductive complex with Cys upon soaking as in rSCL, we observed the partial formation of a C388 persulfide after extended incubation of hSCL crystals with Cys. In Ginsenoside-F4 addition, the stopped-flow data with hSCL and the variant protein with gained CD activity, shown herein, point to a chemical mechanism for the specificity in a step following initial substrate binding, rather than in the substrate binding itself. Still, it cannot be ruled out that several mechanisms work together or that there are mechanistic differences between hSCL and rSCL. In the in vivo scenario, where Cys may bind hSCL and thus block its active site and PLP cofactor availability for catalysis with Sec, other mechanisms e.g. direct protein-protein delivery facilitating Sec binding over Cys may also be in effect. Eukaryotic chromosomes are intricately folded into sophisticated higher-order structures and packaged in the nucleus. These higher-order packaged chromosomes spatially occupy the so-called ��chromosome territory�� in the nucleus and play important roles in genome function and the precise regulation of gene expression. Chromatin loops are ubiquitous sub-structural elements of genome spatial organization. The dynamic nature of nuclear spatial organization is Lomeguatrib highlighted by the mobility of active genes that move from the tightly folded spaces to loop out and relocate, which allows for interaction with other cis-regulatory elements. However, very little is known on how these orchestral components are organized spatially within the nucleus. CCCTC-binding factor is a highly conserved zinc finger protein that is ubiquitously expressed in metazoa. Emerging evidences has revealed that CTCF is a multivalent factor that has been implicated in diverse cellular processes. CTCF is able to recognize and bind to different DNA motifs through different combinations of its eleven zinc-fingers. There are tens of thousands of CTCF binding sites throughout the genomes of human and mouse. By binding to the insulators or boundary elements, CTCF can demarcate chromatin into independent regulatory regions and block communication between promoters and enhancers to regulate gene expression. As the master organizer of genomic spatial organization, CTCF plays important roles in gene transcriptional activation or repression, genomic imprinting, and X chromosome inactivation. The development of high-throughput circular chromosome conformation capture and other related 3C-derived techniques have greatly improved our understanding of the sophisticated organization of the nucleus. In order to explore the roles of CTCF-mediated chromosomal interactions, a highly conserved CTCF binding site was identified by analyzing the data previously reported. This CTCF binding site was used as 4C bait for the screening of potential interacting partners throughout the genome.