Bacteriophage therapy for the treatment of Mycobacterium tuberculosis infections in humanized mice.

The continuing emergence of new strains of antibiotic-resistant bacteria has renewed interest in phage therapy; however, there has been limited progress in applying phage therapy to multi-drug resistant Mycobacterium tuberculosis (Mtb) infections. In this study, we show that bacteriophage strains D29 and DS6A can efficiently lyse Mtb H37Rv in 7H10 agar plates. However, only phage DS6A efficiently kills H37Rv in liquid culture and in Mtb-infected human primary macrophages. We further show in subsequent experiments that, after the humanized mice were infected with aerosolized H37Rv, then treated with DS6A intravenously, the DS6A treated mice showed increased body weight and improved pulmonary function relative to control mice. Furthermore, DS6A reduces Mtb load in mouse organs with greater efficacy in the spleen. These results demonstrate the feasibility of developing phage therapy as an effective therapeutic against Mtb infection.

Efficacy of endoscopic gallbladder drainage in patients with acute cholecystitis.

BACKGROUND: Early cholecystectomy is recommended for patients with acute cholecystitis. However, emergency surgery may not be indicated due to complications and disease severity. Patients requiring drainage are usually treated with percutaneous transhepatic gallbladder drainage (PTGBD), whereas patients with biliary duct stones undergo endoscopic stones removal followed by endoscopic gallbladder drainage (EGBD). Herein, we investigated the efficacy of EGBD in patients with acute cholecystitis. METHODS: Overall, 101 patients receiving laparoscopic cholecystectomy between September 2019 and September 2020 in our department were retrospectively analyzed. RESULTS: The patients (n = 101) were divided into three groups: control group that did not undergo drainage (n = 68), a group that underwent EGBD (n = 7), and a group that underwent PTGBD (n = 26). Median surgery time was 107, 166, and 143 min, respectively. Control group had a significantly shorter surgery time, whereas it did not significantly differ between EGBD and PTGBD groups. The median amount of bleeding was 5 g, 7 g, and 7.5 g, respectively, and control group had significantly less bleeding than the drainage group. We further divided patients into the following subgroups: patients requiring a 5 mm clip to ligate the cystic duct, patients requiring a 10 mm clip due to the thickness of the cystic duct, patients requiring an automatic suturing device, and patients undergoing subtotal cholecystectomy due to impossible cystic duct ligation. There was no significant difference between EGBD and PTGBD regarding the clip used or the need for an automatic suturing device and subtotal cholecystectomy. CONCLUSIONS: There was no significant difference between EGBD and PTGBD groups regarding surgery time or bleeding amount when surgery was performed after gallbladder drainage for acute cholecystitis. Therefore, EGBD was considered a useful preoperative drainage method requiring no drainage bag.

Myo5b Transports Fibronectin-Containing Vesicles and Facilitates FN1 Secretion from Human Pleural Mesothelial Cells.

Pleural mesothelial cells (PMCs) play a central role in the progression of pleural fibrosis. As pleural injury progresses to fibrosis, PMCs transition to mesenchymal myofibroblast via mesothelial mesenchymal transition (MesoMT), and produce extracellular matrix (ECM) proteins including collagen and fibronectin (FN1). FN1 plays an important role in ECM maturation and facilitates ECM-myofibroblast interaction, thus facilitating fibrosis. However, the mechanism of FN1 secretion is poorly understood. We report here that myosin 5b (Myo5b) plays a critical role in the transportation and secretion of FN1 from human pleural mesothelial cells (HPMCs). TGF-ß significantly increased the expression and secretion of FN1 from HPMCs and facilitates the close association of Myo5B with FN1 and Rab11b. Moreover, Myo5b directly binds to GTP bound Rab11b (Rab11b-GTP) but not GDP bound Rab11b. Myo5b or Rab11b knockdown via siRNA significantly attenuated the secretion of FN1 without changing FN1 expression. TGF-ß also induced Rab11b-GTP formation, and Rab11b-GTP but not Rab11b-GDP significantly activated the actin-activated ATPase activity of Myo5B. Live cell imaging revealed that Myo5b- and FN1-containing vesicles continuously moved together in a single direction. These results support that Myo5b and Rab11b play an important role in FN1 transportation and secretion from HPMCs, and consequently may contribute to the development of pleural fibrosis.

Mitochondria-associated myosin 19 processively transports mitochondria on actin tracks in living cells.

Mitochondria are fundamentally important in cell function, and their malfunction can cause the development of cancer, cardiovascular disease, and neuronal disorders. Myosin 19 (Myo19) shows discrete localization with mitochondria and is thought to play an important role in mitochondrial dynamics and function; however, the function of Myo19 in mitochondrial dynamics at the cellular and molecular levels is poorly understood. Critical missing information is whether Myo19 is a processive motor that is suitable for transportation of mitochondria. Here, we show for the first time that single Myo19 molecules processively move on actin filaments and can transport mitochondria in cells. We demonstrate that Myo19 dimers having a leucine zipper processively moved on cellular actin tracks in demembraned cells with a velocity of 50 to 60 nm/s and a run length of ∼0.4 µm, similar to the movement of isolated mitochondria from Myo19 dimer-transfected cells on actin tracks, suggesting that the Myo19 dimer can transport mitochondria. Furthermore, we show single molecules of Myo19 dimers processively moved on single actin filaments with a large step size of ∼34 nm. Importantly, WT Myo19 single molecules without the leucine zipper processively move in filopodia in living cells similar to Myo19 dimers, whereas deletion of the tail domain abolished such active movement. These results suggest that Myo19 can processively move on actin filaments when two Myo19 monomers form a dimer, presumably as a result of tail-tail association. In conclusion, Myo19 molecules can directly transport mitochondria on actin tracks within living cells.

Myocardin Is Involved in Mesothelial-Mesenchymal Transition of Human Pleural Mesothelial Cells.

Pleural fibrosis is characterized by severe inflammation of the pleural space and pleural reorganization. Subsequent thickening of the visceral pleura contributes to lung stiffness and impaired lung function. Pleural mesothelial cells (PMCs) can become myofibroblasts via mesothelial-mesenchymal transition (MesoMT) and contribute to pleural organization, fibrosis, and rind formation. However, the mechanisms that underlie MesoMT remain unclear. Here, we investigated the role of myocardin in the induction of MesoMT. Transforming growth factor ß (TGF-ß) and thrombin induced MesoMT and markedly upregulated the expression of myocardin, but not myocardin-related transcription factor A (MRTF-A) or MRTF-B, in human PMCs (HPMCs). TGF-ß stimulation notably induced the nuclear translocation of myocardin in HPMCs, whereas nuclear translocation of MRTF-A and MRTF-B was not observed. Several genes under the control of myocardin were upregulated in cells undergoing MesoMT, an effect that was accompanied by a dramatic cytoskeletal reorganization of HPMCs consistent with a migratory phenotype. Myocardin gene silencing blocked TGF-ß- and thrombin-induced MesoMT. Although myocardin upregulation was blocked, MRTF-A and MRTF-B were unchanged. Myocardin, α-SMA, calponin, and smooth muscle myosin were notably upregulated in the thickened pleura of carbon black/bleomycin and empyema mouse models of fibrosing pleural injury. Similar results were observed in human nonspecific pleuritis. In a TGF-ß mouse model of pleural fibrosis, PMC-specific knockout of myocardin protected against decrements in lung function. Further, TGF-ß-induced pleural thickening was abolished by PMC-specific myocardin knockout, which was accompanied by a marked reduction of myocardin, calponin, and α-SMA expression compared with floxed-myocardin controls. These novel results show that myocardin participates in the development of MesoMT in HPMCs and contributes to the pathogenesis of pleural organization and fibrosis.

Successful Treatment of Streptococcal Toxic Shock Syndrome with Both Diffuse Peritonitis and Necrotizing Fasciitis.

Streptococcal toxic shock syndrome (STSS) is a life-threatening disease caused by infection of beta-hemolytic streptococci. Here, we report an uncommon case of STSS with both diffuse peritonitis and necrotizing fasciitis and summarize previous cases. The patient was diagnosed with STSS due to an infection of the soft tissue of the lower extremity after surgery for diffuse peritonitis. The general condition had rapidly deteriorated with multiple organ dysfunction. Immediate intensive care, including mechanical ventilation, hemodiafiltration, and repeated debridement, is indispensable for a favorable outcome.

Differences between first-generation and second-generation drug-eluting stent regarding in-stent neoatherosclerosis characteristics: an optical coherence tomography analysis.

We compared first-generation and second-generation drug-eluting stent (DES) with respect to neoatherosclerosis using optical coherence tomography or optical frequency domain imaging. In-stent restenoses in 102 first-generation and 114 second-generation DES were retrospectively assessed. Neoatherosclerosis, which was defined as the presence of lipid-laden neointima or calcification inside a stent, was observed in 33 (27.2%) and 31 (32.4%) lesions in the first-generation and second-generation DES respectively. In the first-generation DES group, the lipid length was significantly longer (5.5 ± 3.8 vs. 3.1 ± 2.1 mm, P = 0.0007), the lipid arc was significantly larger (324 ± 70° vs. 250 ± 94°, P = 0.002), the prevalence of a 360° lipid arc was significantly greater (58 vs. 31%, P = 0.03), and the fibrous cap was significantly thinner (153 ± 85 vs. 211 ± 95 µm, P = 0.02) compared with those in the second-generation DES group. These differences remained significant after adjusting for the age of the stent (lipid length: P < 0.001; lipid arc: P = 0.019; and fibrous cap thickness: P < 0.001). The proliferation course and stability of neoatherosclerosis over time might be superior in second-generation DES.

Simple classification and clinical outcomes of angiographic dissection after balloon angioplasty for femoropopliteal disease.

OBJECTIVE: Angiographic dissection is considered to be associated with restenosis. However, little is known about the impact of the severity of angiographic dissection on future restenosis. METHODS: A total of 319 consecutive de novo femoropopliteal lesions were treated by balloon angioplasty alone. All of these lesions were divided into three groups: group A, no angiographic dissection; group B, mild dissection, the width of the dissection was less than one-third of the lumen; and group C, severe dissection, the width of the dissection was more than one-third of the lumen. Kaplan-Meier analysis estimated the primary patency rate at 3 years between the groups. RESULTS: The primary patency rates at 3 years were 66.0% in group A, 63.8% in group B, and 32.5% in group C (log-rank, P < .001). Cox proportional hazards analysis revealed that a lesion length >100 mm (hazard ratio, 1.734; 95% confidence interval, 1.099-2.735; P = .018) and severe angiographic dissection (hazard ratio, 1.956; 95% confidence interval, 1.276-2.997; P = .002) were predictors of primary patency loss at 3 years. When the lesions were divided into two groups according to the lesion length >100 mm or not, angiographic dissection had a larger impact on restenosis in a long lesion >100 mm (≤100 mm: 65.5% in group A, 75.6% in group B, and 48.0% in group C [log-rank, P = .015]; >100 mm: 68.8% in group A, 42.5% in group B, and 24.2% in group C [log-rank, P = .017]). CONCLUSIONS: Severe angiographic dissection was associated with future restenosis after balloon angioplasty for femoropopliteal lesions, but mild angiographic dissection was not. Angiographic dissection had more impact on future restenosis particularly in treated long lesions. Stents might not be necessary in short lesions with mild dissection.

Myosin X is recruited to nascent focal adhesions at the leading edge and induces multi-cycle filopodial elongation.

Filopodia protrude from the leading edge of cells and play important roles in cell motility. Here we report the mechanism of myosin X (encoded by Myo10)-induced multi-cycle filopodia extension. We found that actin, Arp2/3, vinculin and integrin-ß first accumulated at the cell's leading edge. Myosin X was then gathered at these sites, gradually clustered by lateral movement, and subsequently initiated filopodia formation. During filopodia extension, we found the translocation of Arp2/3 and integrin-ß along filopodia. Arp2/3 and integrin-ß then became localized at the tip of filopodia, from where myosin X initiated the second extension of filopodia with a change in extension direction, thus producing long filopodia. Elimination of integrin-ß, Arp2/3 and vinculin by siRNA significantly attenuated the myosin-X-induced long filopodia formation. We propose the following mechanism. Myosin X accumulates at nascent focal adhesions at the cell's leading edge, where myosin X promotes actin convergence to create the base of filopodia. Then myosin X moves to the filopodia tip and attracts integrin-ß and Arp2/3 for further actin nucleation. The tip-located myosin X then initiates the second cycle of filopodia elongation to produce the long filopodia.

Human myosin VIIa is a very slow processive motor protein on various cellular actin structures.

Human myosin VIIa (MYO7A) is an actin-linked motor protein associated with human Usher syndrome (USH) type 1B, which causes human congenital hearing and visual loss. Although it has been thought that the role of human myosin VIIa is critical for USH1 protein tethering with actin and transportation along actin bundles in inner-ear hair cells, myosin VIIa's motor function remains unclear. Here, we studied the motor function of the tail-truncated human myosin VIIa dimer (HM7AΔTail/LZ) at the single-molecule level. We found that the HM7AΔTail/LZ moves processively on single actin filaments with a step size of 35 nm. Dwell-time distribution analysis indicated an average waiting time of 3.4 s, yielding ∼0.3 s-1 for the mechanical turnover rate; hence, the velocity of HM7AΔTail/LZ was extremely slow, at 11 nm·s-1 We also examined HM7AΔTail/LZ movement on various actin structures in demembranated cells. HM7AΔTail/LZ showed unidirectional movement on actin structures at cell edges, such as lamellipodia and filopodia. However, HM7AΔTail/LZ frequently missed steps on actin tracks and exhibited bidirectional movement at stress fibers, which was not observed with tail-truncated myosin Va. These results suggest that the movement of the human myosin VIIa motor protein is more efficient on lamellipodial and filopodial actin tracks than on stress fibers, which are composed of actin filaments with different polarity, and that the actin structures influence the characteristics of cargo transportation by human myosin VIIa. In conclusion, myosin VIIa movement appears to be suitable for translocating USH1 proteins on stereocilia actin bundles in inner-ear hair cells.

Total thoracoscopic left ventricular lead implantation for hybrid cardiac resynchronization therapy in pacemaker-mediated cardiomyopathy.

Cardiac resynchronization therapy (CRT) has been increasingly performed in patients having heart failure with dyssynchrony. We report a successful case of total thoracoscopic left ventricular (LV) lead implantation in CRT. A 77-year-old man with marked dyssynchrony of the LV wall motion and a low ejection fraction (EF17%) due to pacemaker-mediated cardiomyopathy was referred to us. CRT was planned, but percutaneous LV lead implantation proved difficult owing to anatomical variations. The LV lead was placed in the post-lateral wall of the LV base using a total thoracoscopic procedure. Preoperative dyspnea and dyssynchrony were clearly improved. In CRT, the LV wall stimulation site is important. The LV lead should be implanted in the latest activation area, which can be detected using speckle tracking echocardiography. Surgical lead implantation can be performed in the ideal area, and this procedure may play a new role as a hybrid CRT.

Comparison of first- and second-generation drug-eluting stent efficacies for treating left main and/or three-vessel disease: a propensity matched study.

The efficacy of second-generation drug-eluting stent (DES) for the treatment of left main disease (LM) and/or three vessel disease (3VD) remains unclear. We compared 2-year outcomes of second- versus first -generation DES implantation among patients with LM and/or 3VD and to assess the differential of risk by complexity of coronary artery disease using synergy between percutaneous coronary intervention with taxus and cardiac surgery (SYNTAX) scores. Between April 2007 and December 2012, 341 patients with LM and/or 3VD were treated by percutaneous coronary intervention; 154 with first-generation DES and 137 with second-generation DES. After propensity matching, 101 patients remained in each group. The rate of target lesion revascularization (TLR) and major adverse cardiac event (MACE) were compared. TLR and MACE at 2 years were more common in the first- compared with second-generation DES group (TLR 19.8 vs. 8.9 %; p = 0.016, MACE 24.8 vs. 10.9 %; p = 0.008). In patients with low (0-22) and intermediate (23-32) SYNTAX scores, TLR and MACE tended to occur more often with first-generation DES group. In patients with high SYNTAX scores (≧33), TLR and MACE were significantly more common with first-generation DES group (TLR 29.0 vs. 11.1 %; p = 0.035, MACE 35.5 vs. 13.9 %; p = 0.034). Compared with first-generation DES, second-generation DES proved beneficial in reducing risk of TLR and MACE in patients with LM and/or 3VD, particularly among those with high SYNTAX scores (≧33).

Structure and Regulation of the Movement of Human Myosin VIIA.

Human myosin VIIA (HM7A) is responsible for human Usher syndrome type 1B, which causes hearing and visual loss in humans. Here we studied the regulation of HM7A. The actin-activated ATPase activity of full-length HM7A (HM7AFull) was lower than that of tail-truncated HM7A (HM7AΔTail). Deletion of the C-terminal 40 amino acids and mutation of the basic residues in this region (R2176A or K2179A) abolished the inhibition. Electron microscopy revealed that HM7AFull is a monomer in which the tail domain bends back toward the head-neck domain to form a compact structure. This compact structure is extended at high ionic strength or in the presence of Ca(2+). Although myosin VIIA has five isoleucine-glutamine (IQ) motifs, the neck length seems to be shorter than the expected length of five bound calmodulins. Supporting this observation, the IQ domain bound only three calmodulins in Ca(2+), and the first IQ motif failed to bind calmodulin in EGTA. These results suggest that the unique IQ domain of HM7A is important for the tail-neck interaction and, therefore, regulation. Cellular studies revealed that dimer formation of HM7A is critical for its translocation to filopodial tips and that the tail domain (HM7ATail) markedly reduced the filopodial tip localization of the HM7AΔTail dimer, suggesting that the tail-inhibition mechanism is operating in vivo. The translocation of the HM7AFull dimer was significantly less than that of the HM7AΔTail dimer, and R2176A/R2179A mutation rescued the filopodial tip translocation. These results suggest that HM7A can transport its cargo molecules, such as USH1 proteins, upon release of the tail-dependent inhibition.

Vascular elastography: a novel method to characterize occluded lower limb arteries prior to endovascular therapy.

PURPOSE: To examine the effectiveness of vascular elastography (VE) for the assessment of totally occluded lower limb arteries prior to endovascular treatment (EVT). METHODS: Of 812 consecutive patients who underwent EVT between April 2010 and April 2012, VE was used to evaluate the hardness of chronic total occlusions of the femoropopliteal segment prior to EVT in 65 consecutive patients (48 men; mean 73.9 years, range 63-86). Elastograms of the CTOs proximally and distally were scored using a 5-point scale, and outcomes in limbs with hard lesions (VE score 0-2) were compared to those with soft lesions (VE score 3-4) according to lesion length. The interventionists who performed the endovascular procedures were not informed of the VE score results. RESULTS: CTO characteristics could be evaluated in all cases. A VE score ≤2 was found in 14 of the 23 lesions <150 mm in length. A flexible guidewire was sufficient for recanalization in more of the soft lesions than in the hard lesions [6/9 vs. 2/14, respectively]. In 39 lesions >150 mm, a VE score of 3 was recorded in most lesions proximally, while lesions distally were hard in many cases (VE score 1 or 2). A flexible guidewire alone was sufficient in many soft CTOs (8/13, p<0.01). In 16 cases, hard calcified plaque was indicated by difficulty in penetrating the lesion even with a stiff guidewire; all these cases had a VE score of 1 or 2. A retrograde approach was required only in hard CTOs (p<0.01). The procedure time was significantly longer for the hard lesion group (152.9±63.2 vs. 87.0±29.8 minutes, p=0.001). In 11 in-stent occlusions, only VE scores of 3 (n=4) or 4 (n=7) were recorded, indicating soft thrombus, which was aspirated under distal protection in 7 cases. CONCLUSION: VE may be a useful method for determining the hardness of CTO lesions noninvasively before endovascular therapy, providing information that can help plan the procedure.

Phospholipid-dependent regulation of the motor activity of myosin X.

Myosin X is involved in the reorganization of the actin cytoskeleton and protrusion of filopodia. Here we studied the molecular mechanism by which bovine myosin X is regulated. The globular tail domain inhibited the motor activity of myosin X in a Ca(2+)-independent manner. Structural analysis revealed that myosin X is monomeric and that the band 4.1-ezrin-radixin-moesin (FERM) and pleckstrin homology (PH) domains bind to the head intramolecularly, forming an inhibited conformation. Binding of phosphatidylinositol-3,4,5-triphosphate (PtdIns(3,4,5)P(3)) to the PH domain reversed the tail-induced inhibition and induced the formation of myosin X dimers. Consistently, disruption of the binding of PtdIns(3,4,5)P(3) attenuated the translocation of myosin X to filopodial tips in cells. We propose the following mechanism: first, the tail inhibits the motor activity of myosin X by intramolecular head-tail interactions to form the folded conformation; second, phospholipid binding reverses the inhibition and disrupts the folded conformation, which induces dimer formation, thereby activating the mechanical and cargo transporter activity of myosin X.

Cargo binding activates myosin VIIA motor function in cells.

Myosin VIIA, thought to be involved in human auditory function, is a gene responsible for human Usher syndrome type 1B, which causes hearing and visual loss. Recent studies have suggested that it can move processively if it forms a dimer. Nevertheless, it exists as a monomer in vitro, unlike the well-known two-headed processive myosin Va. Here we studied the molecular mechanism, which is currently unknown, of activating myosin VIIA as a cargo-transporting motor. Human myosin VIIA was present throughout cytosol, but it moved to the tip of filopodia upon the formation of dimer induced by dimer-inducing reagent. The forced dimer of myosin VIIA translocated its cargo molecule, MyRip, to the tip of filopodia, whereas myosin VIIA without the forced dimer-forming module does not translocate to the filopodial tips. These results suggest that dimer formation of myosin VIIA is important for its cargo-transporting activity. On the other hand, myosin VIIA without the forced dimerization module became translocated to the filopodial tips in the presence of cargo complex, i.e., MyRip/Rab27a, and transported its cargo complex to the tip. Coexpression of MyRip promoted the association of myosin VIIA to vesicles and the dimer formation. These results suggest that association of myosin VIIA monomers with membrane via the MyRip/Rab27a complex facilitates the cargo-transporting activity of myosin VIIA, which is achieved by cluster formation on the membrane, where it possibly forms a dimer. Present findings support that MyRip, a cargo molecule, functions as an activator of myosin VIIA transporter function.

Long-term outcome of percutaneous transluminal coronary intervention for chronic total occlusion in the BMS era in Japan.

To investigate the long-term outcome of Percutaneous transluminal intervention (PCI) for chronic total occlusion (CTO). The subjects were 606 patients (1,145 lesions) who were treated for CTO between January 1996 and December 2003 at our institution. Among them, 436 patients with early success and confirmed patency at the CTO by follow-up coronary angiography after 6 months were classified as the patent group (Group P), while 170 patients without early success or with occlusion on follow-up angiography were classified as the occluded group (Group O). In April 2006 (mean: 660 ± 602 days), the outcome of CTO was investigated and the major adverse cardiac events (MACE)-free rate was calculated. Multivariate analysis was performed to identify determinants of death. The early success rate was 76.4% before 2003 when Conquest guidewires were not available. However, it subsequently showed significant improvement to 89%. The cumulative survival rate was significantly higher for Group P (92%) than for Group O (64%) and the MACE-free rate (free from, death, bypass surgery, myocardial infarction, and revascularization) showed a similar trend. The cumulative survival rate of patients without myocardial viability in the territory of the vessel with CTO was significantly higher for Group P (88%) than for Group O (55%). The outcome was significantly worse for patients with occlusion of other vessels (90%) than for patients without additional occlusion (42%). It was significantly better when the left ventricular ejection fraction (LVEF) was ≥40% than when the LVEF was ≤40% (90 vs. 68%). Multivariate analysis identified occluded CTO, other vessel occlusion, low ejection fraction (EF), unimproved EF, and old age as determinants of death from CTO. If early success is obtained and patency is maintained, the long-term outcome after PCI for CTO is significantly better than when failure occurs Occluded CTO, other vessel occlusion, low EF, unimproved EF, and old age are important determinants of the outcome.

The tail binds to the head-neck domain, inhibiting ATPase activity of myosin VIIA.

Myosin VIIA is an unconventional myosin, responsible for human Usher syndrome type 1B, which causes hearing and visual loss. Here, we studied the molecular mechanism of regulation of myosin VIIA, which is currently unknown. Although it was originally thought that myosin VIIA is a dimeric myosin, our electron microscopic (EM) observations revealed that full-length Drosophila myosin VIIA (DM7A) is a monomer. Interestingly, the tail domain markedly inhibits the actin-activated ATPase activity of tailless DM7A at low Ca(2+) but not high Ca(2+). By examining various deletion constructs, we found that deletion of the distal IQ domain, the C-terminal region of the tail, and the N-terminal region of the tail abolishes the tail-induced inhibition of ATPase activity. Single-particle EM analysis of full-length DM7A at low Ca(2+) suggests that the tail folds back on to the head, where it contacts both the motor core domain and the neck domain, forming an inhibited conformation. We concluded that unconventional myosin that may be present a monomer in the cell can be regulated by intramolecular interaction of the tail with the head.