Visualization of an unstable coiled coil from the scallop myosin rod.

Alpha-helical coiled coils in muscle exemplify simplicity and economy of protein design: small variations in sequence lead to remarkable diversity in cellular functions. Myosin II is the key protein in muscle contraction, and the molecule's two-chain alpha-helical coiled-coil rod region--towards the carboxy terminus of the heavy chain--has unusual structural and dynamic features. The amino-terminal subfragment-2 (S2) domains of the rods can swing out from the thick filament backbone at a hinge in the coiled coil, allowing the two myosin 'heads' and their motor domains to interact with actin and generate tension. Most of the S2 rod appears to be a flexible coiled coil, but studies suggest that the structure at the N-terminal region is unstable, and unwinding or bending of the alpha-helices near the head-rod junction seems necessary for many of myosin's functional properties. Here we show the physical basis of a particularly weak coiled-coil segment by determining the 2.5-A-resolution crystal structure of a leucine-zipper-stabilized fragment of the scallop striated-muscle myosin rod adjacent to the head-rod junction. The N-terminal 14 residues are poorly ordered; the rest of the S2 segment forms a flexible coiled coil with poorly packed core residues. The unusual absence of interhelical salt bridges here exposes apolar core atoms to solvent.

Epidermolysis bullosa simplex with mottled pigmentation - mutation analysis proved the diagnosis in a four-generation pedigree.

Epidermolysis bullosa simplex with mottled pigmentation (EBS-MP) is a rare variant of the basal form of EBS, characterized by mild intraepidermal blistering due to lysis of basal keratinocytes and with a progressive reticular hyperpigmentation on the trunk and extremities. A limited number of cases - to date twenty unrelated families - have been published from all over the world, including thirteen reports from Europe. We here report the first Hungarian case in a four generation pedigree with EBS-MP symptoms and prove the diagnosis by mutation analysis. A heterozygous p.Pro25Leu mutation in the first exon of KRT5, together with the heterozygous polymorphism p.Gly138Glu, was identified in all the five affected family members studied. Our report extends the limited number of EBS-MP cases and gives further evidence that KRT5 mutations are responsible for this rare phenotype.

Searching for foreign antigens as possible triggering factors of autoimmunity: Torque Teno virus DNA prevalence is elevated in sera of patients with bullous pemphigoid.

OBJECTIVE: The Torque Teno virus (TTV), a member of virus genus Anellovirus has been shown to be commonly present in humans, yet without detectable pathogenicity. Recent studies imply that TTV may contribute to provoke autoimmune progresses in systemic lupus erythematosus and idiopathic inflammatory myopathies. We aimed to study the presence of TTV in a group of patients with autoimmune bullous diseases with a further goal to identify long-lasting foreign antigen, such as TTV as possible triggers of skin-specific autoimmunity. PATIENTS AND METHODS: We performed in silico research to study similarities between known TTV sequences and antigens of bullous pemphigoid (BP), pemphigus vulgaris (PV) and dermatitis herpetiformis (DH). Basic Local Alignment Search Tool results showed matching regions for the major BP antigens BP180 and BP230, PV antigen desmoglein 3 and DH antigen transglutaminase 3 and disclosed overlapping, antigen-predicted sequences only for BP180 regions. We also assessed the prevalence of TTV in these disorders and compared them with the results from two healthy blood donor groups (group 1: sex- and age-matched for the general bullous group, n = 95; group 2: sex- and age-matched for BP, n = 50). Furthermore, we assayed lymphocytes from four TTV DNA and BP180 NC16A blot-positive BP patients and three controls in a standard lymphocyte transformation test with a TTV peptide from the conserved ORF(Open Reading Frame)1/N22 region. RESULTS: We found that the detection rate of TTV was comparable with that in healthy controls in the group of PV (19/33); whereas detection rates in DH showed a slight, but not significant tendency for elevation (17/20). Contrary, the TTV prevalence in BP patients was significantly elevated (group 1: 36/40 vs group 2: 31/50, P < 0.032). Lymphocytes from all four virus-positive BP patients heavily reacted to TTV peptide while two of the three healthy controls have shown not to recognize the viral sequences. Only the TTV carrier healthy control had a minor reaction at lowest peptide concentration. The combined in silico, polymerse chain reaction and in vitro cell assay data of the present study indicate that a TTV persistence may contribute to the pathogenesis of BP.

Detection of TT virus in patients with idiopathic inflammatory myopathies.

The TT virus, a recently identified single-stranded DNA virus with unknown pathogenicity, has been shown to commonly infect humans. Viruses have been considered to contribute to disease pathogenesis in autoimmune disorders including idiopathic inflammatory myopathies (IIMs) and rheumatoid arthritis (RA). We assessed the prevalence of TTV infection in IIM compared with that in patients with RA and healthy blood donors. Detection of TTV was conducted by nested PCR and real-time PCR in the sera of 94 patients with IIM, 95 RA patients. and 95 age- and sex-matched healthy blood donors. Identity of the PCR products was confirmed by sequencing. TTV DNA was detected in 61 of 94 (64.9%) patients with IIM, in 64 of 95 (67.4%) patients with RA, and in 62 of 95 (65.3%; P > 0.05) healthy individuals. Age, sex, activity, or duration of disease had no influence on TTV positivity in either group. However, patients with severe IIM (n = 36) had a significantly higher rate of TTV infection (31/36, 86.1%) than patients with mild disease (30/58, 51.7%, P < 0.05, chi(2) = 10.0). Disease was considered severe in IIM when immunosuppressive treatment was necessary because of continuous high activity and/or serious inner-organ involvement despite corticosteroid treatment. In conclusion, although we found the detection rate of TTV similar in patients with idiopathic inflammatory myopathies and rheumatoid arthritis and comparable to that in healthy controls, our data suggest that infection with TT virus may result in a more severe disease in patients with idiopathic inflammatory myopathies.

Increased prevalence of transfusion-transmitted virus and cross-reactivity with immunodominant epitopes of the HRES-1/p28 endogenous retroviral autoantigen in patients with systemic lupus erythematosus.

OBJECTIVE: Systemic lupus erythematosus (SLE) patients produce autoantibodies to HRES-1/p28, a human endogenous retrovirus-encoded nuclear protein. To identify cross-reactive viral antigens capable of triggering autoreactivity, HRES-1/p28 epitopes were mapped by SLE antibodies. METHODS: Forty-four peptides overlapping HRES-1/p28 and 13 viral peptides were synthesized on cellulose membrane and tested for recognition by antibodies from 16 HRES-1 Western blot seropositive SLE patients. Transfusion-transmitted virus (TTV) was detected by gene amplification in sera of 211 SLE patients, 78 healthy SLE family members, 199 unrelated healthy donors, and 91 rheumatoid arthritis (RA) patients. RESULTS: HRES-1/p28 residues 41-55, 121-135, and 156-170 were recognized by 12/16 (75.0%), 11/16 (68.8%), and 9/16 lupus sera (56.25%) and considered immunodominant. HRES-1/p28 residues 121-135 harbor cross-reactive epitope with retroviral peptides and the 70 K U1snRNP lupus autoantigen. HRES-1/p28 residues 41-55 and 156-170 exhibited the highest prevalence of cross-reactivity with TTV peptide ORF2a (14/16, 87%). Prevalence of TTV DNA was increased in lupus patients (120/211) with respect to healthy (66/199; P < 0.0001) or RA controls (23/91; P < 0.0001). TTV prevalence in healthy lupus relatives (40/78) was decreased with respect to lupus patients (80/121; P = 0.0184) and increased with respect to unrelated healthy donors (66/199; P = 0.0026). HRES-1/p28 Western blot reactivity was observed in 12/23 TTV PCR-negative donors and 43/58 TTV PCR-positive donors (P < 0.0281). CONCLUSIONS: Increased prevalence of TTV and molecular mimicry with HRES-1/p28 may contribute to generation of antinuclear antibodies and pathogenesis of SLE.