J W Cheung | PubMed Health

PubMed2003

Two factor XI mutations in a Chinese family with factor XI deficiency.

We describe a Chinese family with factor XI deficiency, the first reported to date. The proband had factor XI activity of 1% and was heterozygous for two nonsense mutations, an exon-8 C713-->T mutation resulting in Gln263-->Term, and an exon-10 C979-->A mutation resulting in Tyr351-->Term. Two daughters were heterozygous for the Gln263-->Term mutation and two for the Try351-->Term mutation. All showed a reduction of factor XI activity to about 50%. The Gln263-->Term mutation has been described in two Japanese families, and it remains to be determined whether a common founder exists between the three kindreds. The Try351-->Term mutation is novel.

Asian People↗

PubMed1997

SKN-1 domain folding and basic region monomer stabilization upon DNA binding.

The SKN-1 transcription factor specifies early embryonic cell fates in Caenorhabditis elegans. SKN-1 binds DNA at high affinity as a monomer, by means of a basic region like those of basic-leucine zipper (bZIP) proteins, which bind DNA only as dimers. We have investigated how the SKN-1 DNA-binding domain (the Skn domain) promotes stable binding of a basic region monomer to DNA. A flexible arm at the Skn domain amino terminus binds in the minor groove, but a support segment adjacent to the carboxy-terminal basic region can independently stabilize basic region-DNA binding. Off DNA, the basic region and arm are unfolded and, surprisingly, the support segment forms a molten globule of four alpha-helices. On binding DNA, the Skn domain adopts a tertiary structure in which the basic region helix extends directly from a support segment alpha-helix, which is required for binding. The remainder of the support segment anchors this uninterrupted helix on DNA, but leaves the basic region exposed in the major groove. This is similar to how the bZIP basic region extends from the leucine zipper, indicating that positioning and cooperative stability provided by helix extension are conserved mechanisms that promote binding of basic regions to DNA.

Amino Acid Sequence↗