Genes with sequences reminiscent of neuronal K+ channels have recently been identified in prokaryotes. These putative K+ channels appear to be integral membrane proteins, with multiple transmembrane sequences identified by hydrophobicity analysis and a sequence strikingly similar to the pore-lining "P-region" motif found in all known eukaryotic K+ channels. This study examines the oligomeric state and stability in detergent micelles of SliK, a K+ channel homologue from Streptomyces lividans. A synthetic gene for SliK was expressed at high levels in Escherichia coli, and the protein was purified. The predominant form of the protein runs in SDS-PAGE gels as an oligomer of the 19-kDa polypeptide, but harsh treatments such as heat or high pH convert this slowly-migrating material into monomeric form. A "mass-tagging" strategy developed to examine subunit stoichiometry shows that SliK is a homotetramer in SDS and dodecyl maltoside micelles. The tetrameric structure can be disrupted by P-region mutations known to prevent the functional expression of neuronal K+ channels. The tetramer is remarkably stable, showing no conversion to the monomeric form after 14 days at room temperature. Although SliK-mediated cation flux activity was not observed, the tetrameric behavior of the protein argues that SliK may provide a system for a direct attack on the structure of a K+ channel P-region sequence.

Adequate coverage of complex, composite scalp defects in previously radiated, infected, or otherwise compromised tissue represents a challenge in reconstructive surgery. To provide wound closure with bony protection to the brain, improve cranial contour, and prevent or seal cerebrospinal fluid (CSF) leaks, composite free tissue transfer is a reliable and safe option. We report our experience with the latissimus dorsi/rib intercostal perforator myo-osseocutaneous free flap in the reconstruction of bony and soft tissue defects of the cranium and overlying scalp. The surgical technique, design, and outcomes of the latissimus dorsi/rib intercostal perforator myo-osseocutaneous free flap reconstruction in five patients with cranial defects between 2003 and 2007 were retrospectively evaluated. Patient characteristics, defect size, underlying cause, reconstructive details, and complications were analyzed. All patients (age 43 to 81) had composite defects ranging from 36 to 750 cm2 (mean size 230 cm2) for the bony component and from 16 to 400 cm2 (mean size 170 cm2) for the soft tissue defect. All patients had a history of prior or current infection of the affected area, and two patients had a CSF leak. Defects were due to malignancy and infection (n = 2), infiltrative cutaneous mucormycosis with osteomyelitis (n = 1), and hemorrhagic stroke requiring craniectomy (n = 2), complicated by infection and failed cranioplasty in one patient and continuous CSF leak in the other. The latissimus dorsi composite free flap consisting of skin, muscle, and vascularized rib can successfully cover large complex cranial defects, provide skeletal support, improve contour, and significantly enhance functional outcome with limited donor site morbidity.

Indolent rhinocerebral mucormycosis is rare and is seldom survived by immunosuppressed patients. Multimodal therapy with surgical debridement and antifungal chemotherapy is required for an optimal outcome. Discontinuance of immunosuppressive therapy, if possible, is a cornerstone of management.

In an effort to address the high recurrence rate, we describe our aggressive surgical approach, including resection of the hypertrophied gingiva and alveolar processes. Two-staged gingival resection, as opposed to the more traditional 4-stage quadrantectomy approach, has resulted in no recurrence to date, suggesting an improved outcome over the traditional techniques.