[Structural biology of small G proteins].
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Amino Acid Sequence↗
Biomedical subjects
K Ihara
Publications and source records attributed to K Ihara.
[Clinical findings and genetic bases of congenital complement deficiencies].
The clinical findings and genetic bases of inherited deficiencies of plasma complement components and complement control proteins are reviewed. In Japan, since the frequencies of late complement component deficiencies (LCCD) are high, clinical features of neisserial infections associated with LCCD are described in details. C 9 deficiency is one of the most frequent genetic disorders in Japan and most of them are healthy. However, C 9 deficiency is weakly but significantly associated with the development of meningococcal meningitis but not of systemic lupus erythematosus. The common Arg 95 Stop mutation was found in most individuals with C 9 deficiency. Molecular epidemiologic study revealed that homozygous and heterozygous Arg 95 Stop mutation of C 9 gene is found in approximately one of 1000 individuals and one of 15 individuals, respectively. Complement studies including C 9 antigen and DNA analyses should be performed in patients with meningococcal meningitis or recurrent bacterial infections.
Bacterial Infections↗
Functioning muscle transplantation after wide excision of sarcomas in the extremity.
Free functioning muscle transplantation was performed after resection of 23 sarcomas in the extremity. There were 21 soft tissue sarcomas and two malignant bone tumors. The tumor resection was performed with a wide margin in all except two patients who had a marginal margin in a limited area. The consequent extensive soft tissue defect received free musculocutaneous flaps, the motor nerve of which was repaired in the recipient site. The most frequent procedure was latissimus dorsi transplantation to replace thigh muscles in 17 cases. The other donors included gracilis, tensor fascia lata, and rectus femoris, which were selected according to the site of defects. Patients were followed up for a mean of 60 months (range, 13-119 months). The grafted muscles showed reinnervation at a mean of 6 months postoperatively in all patients except for a 75-year-old patient. Obtained contraction of the muscles was powerful in 18 patients and fair in four patients. Performance of the salvaged limb significantly improved after recovery of the muscles. Although there were five distant recurrences, local recurrence was seen in one patient with systemic metastases. Because muscle loss could be compensated functionally for by the innervated free muscle transfer, the method encouraged surgeons to perform more radical tumor excisions and this may have contributed to the excellent local tumor control that was achieved. Thus, functioning muscle transplantation was extremely useful in limb salvage surgery from the functional and oncologic viewpoints.
Adolescent↗
Crystal structure of human RhoA in a dominantly active form complexed with a GTP analogue.
The 2.4-A resolution crystal structure of a dominantly active form of the small guanosine triphosphatase (GTPase) RhoA, RhoAV14, complexed with the nonhydrolyzable GTP analogue, guanosine 5'-3-O-(thio)triphosphate (GTPgammaS), reveals a fold similar to RhoA-GDP, which has been recently reported (Wei, Y., Zhang, Y., Derewenda, U., Liu, X., Minor, W., Nakamoto, R. K., Somlyo, A. V., Somlyo, A. P., and Derewenda, Z. S. (1997) Nat. Struct. Biol. 4, 699-703), but shows large conformational differences localized in switch I and switch II. These changes produce hydrophobic patches on the molecular surface of switch I, which has been suggested to be involved in its effector binding. Compared with H-Ras and other GTPases bound to GTP or GTP analogues, the significant conformational differences are located in regions involving switches I and II and part of the antiparallel beta-sheet between switches I and II. Key residues that produce these conformational differences were identified. In addition to these differences, RhoA contains four insertion or deletion sites with an extra helical subdomain that seems to be characteristic of members of the Rho family, including Rac1, but with several variations in details. These sites also display large displacements from those of H-Ras. The ADP-ribosylation residue, Asn41, by C3-like exoenzymes stacks on the indole ring of Trp58 with a hydrogen bond to the main chain of Glu40. The recognition of the guanosine moiety of GTPgammaS by the GTPase contains water-mediated hydrogen bonds, which seem to be common in the Rho family. These structural differences provide an insight into specific interaction sites with the effectors, as well as with modulators such as guanine nucleotide exchange factor (GEF) and guanine nucleotide dissociation inhibitor (GDI).
Amino Acid Sequence↗
Nonsense mutation in exon 4 of human complement C9 gene is the major cause of Japanese complement C9 deficiency.
Deficiency of the ninth component of human complement (C9) is the most common complement deficiency in Japan but is rare in other countries. We studied the molecular basis of C9 deficiency in four Japanese C9-deficient patients who had suffered from meningococcal meningitis. Direct sequencing of amplified C9 cDNA and DNA revealed a nonsense substitution (CGA-->TGA) at codon 95 in exon 4 in the four C9-deficient individuals. An allele-specific polymerase chain reaction system designed to detect exclusively only one of the normal and mutant alleles indicated that all the four patients were homozygous for the mutation in exon 4 and that the parents of patient 2 were heterozygous. The common mutation at codon 95 in exon 4 might be responsible for most Japanese C9 deficiency.
Adolescent↗
Genomic structure of the human glucose 6-phosphate translocase gene and novel mutations in the gene of a Japanese patient with glycogen storage disease type Ib.
Glycogen storage disease (GSD) type Ib is an autosomal recessive disorder caused by a deficiency in microsomal glucose 6-phosphate (G6P) translocase. A gene mutated in GSD type Ib patients has recently been isolated. We have determined the entire sequence of the human G6P translocase gene by PCR-directed sequencing. The gene spans approximately 5 kb of genomic DNA and contains eight exons. Analysis of DNA from a Japanese patient with GSD type Ib revealed new compound heterozygous mutations; a T to C transition at cDNA position 521 resulting in W118R, and an A to C transversion at the -2 splicing acceptor site of intron 1. Reverse transcription (RT)-PCR from leukocyte RNA of the patient revealed the abnormally spliced transcript. These results further support the suggestion that the gene is causative for GSD Ib and should be useful in the molecular diagnosis of such patients.
Antiporters↗
Tuberculous bursitis of the greater trochanter.
A patient with tuberculous bursitis of the greater trochanter is reported. A 37-year-old woman had experienced persistent dull hip pain and noticed diffuse swelling over the greater trochanteric region. Plain radiograph revealed unremarkable osteopenic changes in the greater trochanter and faint mineralization in the vicinity of the trochanter. Computed tomogram showed erosion of the trochanter and a large soft tissue mass. Magnetic resonance imaging demonstrated a large multicystic mass. Histology of the cyst wall, showing chronic granulomatous tissue, and a positive culture of Mycobacterium tuberculosis confirmed the diagnosis of musculoskeletal tuberculosis. Complete excision of the lesion, followed by 6 months of antituberculous chemotherapy with rifampicin and isoniazid, cured the disease. There has been no sign of recurrent disease in 30 months of follow-up. Correct diagnosis was difficult because of its rarity, but modern imaging technology, magnetic resonance imaging, in particular, was extremely useful for showing the extent of the disease. Tuberculous infection should be considered as a differential diagnosis in patients with persistent hip pain.
Adult↗
High frequency of fusion transcripts of exon 11 and exon 4/5 in AF-4 gene is observed in cord blood, as well as leukemic cells from infant leukemia patients with t(4;11)(q21;q23).
The MLL gene located on chromosome 11q23 and its translocation to the AF-4 gene located on chromosome 4q21 play a pivotal role in leukemogenesis in infancy. Studies of identical leukemic twins have provided evidence of the MLL rearrangement as a fetal event during pregnancy. We analyzed the presence and frequency of the MLL/AF-4 rearrangement in normal cord blood. Although no chimeric mRNA of MLL or AF-4 was detected in 65 cord blood samples, in-frame fusion transcripts of exon 11 and exon 4 or 5 of the AF-4 gene were detected in three of the samples by a nested polymerase chain reaction. When primers of exon 11 and exon 5 of the AF-4 gene were used, two forms of fusion transcripts (AF-4 exon 11/4 or exon 11/5) were detected in 20 of the 65 cord blood samples (31%) and also four of six leukemic cell samples with t(4;11) (67%), whereas such transcripts were not observed in any of 21 peripheral blood samples nor in fetal fibroblasts. These findings suggest that the in-frame fusion of exon 11 and exon 4 or 5 of the AF-4 gene frequently occurs in hematopoietic cells during the intrauterine period, even in a healthy fetus. Although it is unknown whether the proteins of the AF-4 fusion transcripts have some functions, the instability of the AF-4 gene may be associated with the leukemogenesis of infant leukemia.
Chromosomes, Human, Pair 11↗
One-year prognosis of depressive illness in the elderly population in Japan.
A 1-year prospective study of 43 elderly depressed residents (13 men and 30 women) in Nagai City in Japan is described. An initial survey was carried out in 1993 to find depressed residents. The subjects of the survey were 2056 residents of 65 years of age and older. The Japanese version of the Geriatric Depression Scale (GDS) was employed as a screening tool in the first phase of the survey. In the second phase, screened subjects and control subjects were interviewed by psychiatrists using the Structured Interview for DSM-III-R (SCID). The diagnosis of depression was made by the psychiatrists on the basis of the results of the SCID. Forty-three persons were judged to be depressed. At follow-up, 10 were still depressed and 15 were well. Four were demented. Fourteen dropped out due to death, hospitalization, absence from home or refusal. The results showed that approximately half of the elderly depressed persons seemed to recover by the time of the 1-year follow-up. One-year prognosis of dysthymia was the worst. Some types of depression seemed to be a precursor for dementia. The concern is with how the findings may be used as an aid in understanding and planning community mental health services strategies. The results indicate that it is very important to pay close attention to patients with depressive illness who do not meet the criteria for major depression.
Aged↗
Free vascularized fibular grafts for large bone defects in the extremities after tumor excision.
Free vascularized fibular grafts were used in nine selected patients with bone tumors in the involved extremity. There were five locally aggressive tumors and four malignant tumors. Each skeletal defect was longer than 10 cm, and the mean length was 13 cm. Ten grafts of 17.4 cm in mean length were harvested in these nine patients. In two cases with upper-extremity involvement, arthroplasty using the fibular head was the procedure of choice, while interacalary grafting was performed in the lower extremity. Dual grafting was performed for complete defects of the femur. The viability of each graft was demonstrated through survival of the combined skin flaps or with a positive bone scan. Primary bony union was obtained in all cases, and the mean time to union was 5.2 months. In the lower extremity, significant hypertrophy of the graft was seen. Satisfactory functional results were obtained in all the patients.
Adolescent↗
Prevention of hypoglycaemia in a patient with type Ib glycogen storage disease by an amylase (alpha-glucosidase) inhibitor.
Patients with type Ib glycogen storage disease (GSD Ib) are susceptible to hypoglycaemic episodes. To determine whether an amylase (alpha-glucosidase) inhibitor, voglibose, can be useful in the control of hypoglycaemia, we tried it in a 14-y-old male with GSD Ib. Oral administration of voglibose prolonged the duration of normoglycaemia and reduced the incidence of hypoglycaemia attacks. These findings indicate that voglibose may be useful for preventing hypoglycaemia in GSD Ib patients.
Adolescent↗
Limb-sparing surgery in synovial sarcoma of the forearm and lower leg by reinnervated free muscle transfer.
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Adolescent↗
Assignment1 of glucose 6-phosphate translocase (G6PT1) to human chromosome band 11q23.3 by in situ hybridization.
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Antiporters↗
[Prevalence of affective disorders on the basis of DSM-III among the elderly in a rural community in Japan].
The prevalence rates of affective disorders among the elderly in a rural community according to the criteria of the third edition of Diagnostic and Statistical Manual of Mental Disorders were investigated. The survey used a two-phase method which combined a self-administered depression scale and diagnostic interviews by psychiatrists. The subjects were all 766 persons aged 65 years or older in a rural village in Japan. In the first phase, 698 persons completed a self-administered scale, the Center for Epidemiologic Studies Depression scale (CES-D). In the second phase, 83 persons scoring 12 points or more on the CES-D and an additional 8 persons who, for unknown reason, did not respond to the CES-D were assessed by psychiatrists using a modified version of the Diagnostic Interview Schedule. The subjects' physical health and life events, the presence of dementia, and other factors were taken into account when diagnoses were made. The point prevalence rates of depression without dementia as a comorbid condition by category were as follows: major depression, 0.5%; dysthymic disorder, 0.3%; and atypical depression, 0.4%. The point prevalence rates of depression with dementia as a comorbid condition were as follows: major depression, 0.7%; dysthymic disorder, 0.4%; and atypical depression, 0.4%. Major depression was more prevalent in women than in men and was more prevalent in persons aged 75 years of older than in younger subjects.
Aged↗
Crystal structure of PHO4 bHLH domain-DNA complex: flanking base recognition.
The crystal structure of a DNA-binding domain of PHO4 complexed with DNA at 2.8 A resolution revealed that the domain folds into a basic-helix-loop-helix (bHLH) motif with a long but compact loop that contains a short alpha-helical segment. This helical structure positions a tryptophan residue into an aromatic cluster so as to make the loop compact. PHO4 binds to DNA as a homodimer with direct reading of both the core E-box sequence CACGTG and its 3'-flanking bases. The 3'-flanking bases GG are recognized by Arg2 and His5. The residues involved in the E-box recognition are His5, Glu9 and Arg13, as already reported for bHLH/Zip proteins MAX and USF, and are different from those recognized by bHLH proteins MyoD and E47, although PHO4 is a bHLH protein.
Amino Acid Sequence↗
Identification of proteolipid from an extremely halophilic archaeon Halobacterium salinarum as an N,N'-dicyclohexyl-carbodiimide binding subunit of ATP synthase.
ATP synthesis in an extremely halophilic archaeon, Halobacterium salinarum, was inhibited by N-cyclohexyl-N'-[4-(dimethylamino)-alpha-naphthyl]carbodiimide (NCD-4), a fluorescent analog of N,N'-dicyclohexylcarbodiimide (DCCD). By tracing the fluorescent signal, a hydrophobic 8-kDa protein (proteolipid) was purified from the halobacterial membrane as one of the most DCCD-reactive proteins and its N-terminal amino acid sequence was determined. The gene encoding the proteolipid was found in the region upstream of the genes encoding the two major subunits of halobacterial A-type ATPase [K. Ihara and Y.Mukohata (1991) Arch. Biochem. Biophys. 286, 111-116]. Halobacterial proteolipid was more similar in size to the proteolipid of F-type ATPase than that of V-type ATPase. However, multiple amino acid sequence alignment of proteolipids showed a higher degree of relatedness between V-type and A-type ATPase proteolipids. Together with the recent finding of a triplicate proteolipid encoding gene from the methanogenic archaeon Methanococcus jannaschii [C. J. Bult et al. (1996) Science 273, 1058-1073], proteolipids from archaea seem to have diverse characteristics in comparison with those from eubacteria or from eukaryotes.
Adenosine Triphosphatases↗
Significance of the conserved amino acid sequence for human MTH1 protein with antimutator activity.
8-Oxo-7,8-dihydro-2'-deoxyguanosine 5'-triphosphate (8-oxo-dGTP) is produced during normal cellular metabolism, and incorporation into DNA causes transversion mutation. Organisms possess an enzyme, 8-oxo-dGTPase, which catalyzes the hydrolysis of 8-oxo-dGTP to the corresponding nucleoside monophosphate, thereby preventing the occurrence of mutation. There are highly conserved amino acid sequences in prokaryotic and eukaryotic proteins containing this and related enzyme activities. To elucidate the significance of the conserved sequence, amino acid substitutions were introduced by site- directed mutagenesis of the cloned cDNA for human 8-oxo-dGTPase, and the activity and stability of mutant forms of the enzyme were examined. When lysine-38 was replaced by other amino acids, all of the mutants isolated carried the 8-oxo-dGTPase-negative phenotype. 8-Oxo-dGTPase-positive revertants, isolated from one of the negative mutants, carried the codon for lysine. Using the same procedure, the analysis was extended to other residues within the conserved sequence. At the glutamic acid-43, arginine-51 and glutamic acid-52 sites, all the positive revertants isolated carried codons for amino acids identical to those of the wild type protein. We propose that Lys-38, Glu-43, Arg-51 and Glu-52 residues in the conserved region are essential to exert 8-oxo-dGTPase activity.
Amino Acid Sequence↗
Preliminary X-ray studies of a new crystal form of PHO4-DNA complex.
A new crystal form of PHO4 DNA-binding domain-DNA complex was obtained by the truncation of the N-terminal segment. This diffracts to a higher resolution than any forms reported previously. The present crystal belongs to orthorhombic space group P2(1)2(1)2(1), with unit-cell dimensions a=53.51, b=68.30, c= 108.77 A. The crystal contains one protein dimer-DNA complex in the asymmetric unit.
Journal Article↗