Optimization of Temperature Modulation for Gas Classification Based on Bayesian Optimization.

This study proposes an optimization method for temperature modulation in chemiresistor-type gas sensors based on Bayesian optimization (BO), and its applicability was investigated. As voltage for a sensor heater, our previously proposed waveform was employed, and the parameters determining the voltage range were optimized. Employing the Bouldin-Davies index (DBI) as an objective function (OBJ), BO was utilized to minimize the DBI calculated from a feature matrix built from the collected data followed by pre-processing. The sensor responses were measured using five test gases with five concentrations, amounting to 2500 data points per parameter set. After seven trials with four initial parameter sets (ten parameter sets were tested in total), the DBI was successfully reduced from 2.1 to 1.5. The classification accuracy for the test gases based on the support vector machine tends to increase with decreasing the DBI, indicating that the DBI acts as a good OBJ. Additionally, the accuracy itself increased from 85.4% to 93.2% through optimization. The deviation from the tendency that the accuracy increases with decreasing the DBI for some parameter sets was also discussed. Consequently, it was demonstrated that the proposed optimization method based on BO is promising for temperature modulation.

ATP binding promotes light-induced structural changes to the protein moiety of Arabidopsis cryptochrome 1.

Cryptochromes (CRYs) are blue-light receptors involved in photomorphogenesis in plants. Flavin adenine dinucleotide (FAD) is one of the chromophores of cryptochromes; its resting state oxidized form is converted into a signalling state neutral semiquionod radical (FADH˙) form. Studies have shown that cryptochrome 1 from Arabidopsis thaliana (AtCRY1) can bind ATP at its photolyase homology region (PHR), resulting in accumulation of FADH˙ form. This study used light-induced difference Fourier transform infrared spectroscopy to investigate how ATP influences structural changes in AtCRY1-PHR during the photoreaction. In the presence of ATP, there were large changes in the signals from the protein backbone compared with in the absence of ATP. The deprotonation of a carboxylic acid was observed only in the presence of ATP; this was assigned as aspartic acid (Asp) 396 through measurement of Asp to glutamic acid mutants. This corresponds to the protonation state of Asp396 estimated from the reported pKa values of Asp396; that is, the side chain of Asp396 is deprotonated and protonated for the ATP-free and -bound forms, respectively, in our experimental condition at pH8. Therefore, Asp396 acts a proton donor to FAD when it is ptotonated. It was indicated that the protonation/deprotination process of Asp396 is correlated with the accunumulation of FADH˙ and protein conformational changes.

A bio-image sensor for simultaneous detection of multi-neurotransmitters.

We report here a new bio-image sensor for simultaneous detection of spatial and temporal distribution of multi-neurotransmitters. It consists of multiple enzyme-immobilized membranes on a 128 × 128 pixel array with read-out circuit. Apyrase and acetylcholinesterase (AChE), as selective elements, are used to recognize adenosine 5'-triphosphate (ATP) and acetylcholine (ACh), respectively. To enhance the spatial resolution, hydrogen ion (H+) diffusion barrier layers are deposited on top of the bio-image sensor and demonstrated their prevention capability. The results are used to design the space among enzyme-immobilized pixels and the null H+ sensor to minimize the undesired signal overlap by H+ diffusion. Using this bio-image sensor, we can obtain H+ diffusion-independent imaging of concentration gradients of ATP and ACh in real-time. The sensing characteristics, such as sensitivity and detection of limit, are determined experimentally. With the proposed bio-image sensor the possibility exists for customizable monitoring of the activities of various neurochemicals by using different kinds of proton-consuming or generating enzymes.

Development of an ATP and hydrogen ion image sensor using a patterned apyrase-immobilized membrane.

A bio-image sensor using a patterned apyrase-immobilized membrane was developed to visualize the activities of adenosine triphosphate (ATP) and H+ ion in real-time. An enzymatic membrane patterning technique was suggested to immobilize apyrase on a specific sensing area of a charge coupled device (CCD)-type image sensor. It was able to observe the spatiotemporal information of ATP and H+ ion. The smallest size of a patterned membrane is 250×250µm2. The fabrication parameters of the patterned membrane, such as its thickness and the intensity of the incident light used for photolithography, were optimized experimentally. The sensing area under the patterned apyrase-immobilized membrane revealed a linear response up to 0.6mM of ATP concentration with a sensitivity of 37.8mV/mM. Meanwhile, another sensing area without the patterned membrane measured the diffused H+ ion from nearby membranes. This diffusion characteristics were analyzed to determine a measurement time that can minimize the undesirable impact of the diffused ions. In addition, the newly developed bio-image sensor successfully reconstructed ATP and H+ ion dynamics into sequential 2-dimensional images.

Combination of GnRH Antagonist Degarelix and Antiandrogen Is Effective in PSA Reduction and Bone Management in Patients with Prostate Cancer.

OBJECTIVES: To investigate the efficacy of combination treatment of degarelix and antiandrogen in patients with prostate cancer. METHODS: We prospectively investigated the efficacy of combination treatment of degarelix and antiandrogen in 12 patients with treatment-naive prostate cancer. We surveyed PSA, LH, FSH and testosterone at day 3, 7, 14 and 28 during the initial month and thereafter once a month for 1 year. In cases with bone metastasis, we analyzed serum bone markers such as alkaline phosphatase(ALP), bone-type ALP and carboxyterminal telopeptide of type- I collagen once a month. Skeletal related events (SREs) were also monitored. RESULTS: PSA progression free survival was 65%. PSA was reduced from baseline by 80% at day 14 and by 93% at day 28. In all patients serum testosterone immediately reached castrate level at day 3 and was maintained for 1 year without breakthrough escape. Both LH and FSH were reduced to within normal range at day 3. In contrast, all bone markers temporarily increased at day 28, and thereafter decreased. Although 2 patients had suffered from SREs before treatment, there were no SREs after combination treatment. CONCLUSIONS: The present study showed that combination of degarelix and antiandrogen could lead to favorable PSA reduction and immediate castrate level at an earlier phase. However, further study is needed to compare the difference between degarelix monotherapy and these combinations.

[Successful Management by Immunoglobulin for Sunitinib-Induced Thrombocytopenia in a Patient with Advanced Metastatic Renal Cell Carcinoma].

An 81-year-old man was referred to our hospital because of a right renal tumor with vena cava thrombus and multiple lung metastases that were detected by computed tomography (CT) scan during evaluation of respiratory discomfort. We started medical treatment with sunitinib at a dose of 50 mg daily in a 2-week-on, 1-week-off schedule after confirming clear cell renal cell carcinoma by tumor biopsy. After 2-week sunitinib treatment, thrombocytopenia continued and platelet count decreased to 1.8×10(9)/l at day 11 after stopping sunitinib. We needed to administer a total of 60 units platelet transfusion because of persistent thrombocytopenia. Bone marrow aspiration did not reveal myelosuppression or carcinoma invasion to bone marrow. Under the clinical diagnosis of drug-induced thrombocytopenia secondary to sunitinib, we started immunoglobulin therapy at day 23 after stopping sunitinib. Platelet count returned to normal 10 days after starting immunoglobulin. The patient developed exacerbating lung metastasis and carcinomatous lymphangiosis during subsequent course and died of renal cell carcinoma 79 days after starting sunitinib. Thrombocytopenia after sunitinib therapy is often encountered but prolonged thrombocytopenia is rare after stopping sunitinib. This case suggests that immunoglobulin therapy is effective for drug-induced prolonged thrombocytopenia through immunological mechanism.

[A Case Report of Suspected Tuberculous Granuloma in the Kidney after BCG Perfusion Therapy for Urothelial Carcinoma of the Renal Pelvis].

A 66-year-old male patient was referred to our hospital for bilateral renal pelvic tumors. Ureteroscopic biopsy revealed urothelial carcinoma (UC) of low grade (G1) of the renal pelvis. Renal sparing treatment with systemic chemotherapy and percutaneous tumor resection was performed. However, during subsequent follow up, a recurrent tumor was found on the left ureter. After ureteroscopic laser ablation of the tumor, Bacillus Calmette-Guerin (BCG) perfusion therapy (once a week, total 6 weeks) was performed via a single J ureteral catheter with no adverse events. Later, another recurrent recurrence was found on the right ureter, and was managed by ureteroscopic laser ablation followed by BCG perfusion therapy via a single J ureteral catheter. However, the patient developed high fever with chill from the day after initial BCG perfusion therapy on the right side. Although we started antibiotics, high fever continued. Then antituberculous drugs were administered and his condition was improved. Computed tomographic scan revealed a right renal mass 57 mm in diameter, which was consistent with tuberculous granuloma. The tuberculous granuloma persisted despite the continuation of anti-tuberculous drugs. In exceptional cases of upper tract UC such as single kidney and bilateral tumor, BCG perfusion therapy has been used as adjunctive treatment to cure or prevent UC. However, dosages and administration methods of BCG perfusion therapy for upper tract UC still remain to be standardized. Serious adverse events after BCG perfusion therapy require prompt and proper management including the use of anti-tuberculous drugs.

[Perioperative complications of transurethral resection of bladder tumor in patients receiving antithrombotic therapy].

We examined perioperative complications of transurethral resection of bladder tumor (TURBT) in patients receiving antithrombotic therapy. We retrospectively studied 276 patients who underwent TURBT in our institute from January 2007 to March 2013. The study group consisted of 105 patients (38%) who were receiving antithrombotic agents, and the other 171 patients (62%) without antithrombotic agents were assigned to the control group. The period of discontinuation of antithrombotic agents complied with our institutional rule. The most frequently used agent was aspirin (69 patients : 66%), followed by warfarin (25 patients : 24%). Fourteen patients receiving warfarin (56%) needed heparin bridging therapy. There was no significant difference in average operative time (51 minutes versus 54 minutes), or average days to removal of urethral catheter (3.7 days versus 3.3 days) between the study and control groups. Hemorrhagic and ischemic complications were noted in 11 (10.5%) and 2 (1.9%) patients in the study group and 11 (6.4%) and none (0%) of the patients in the control group, respectively, with no significant difference between the 2 groups. However, prevalence of hemorrhagic complications in patients receiving heparin bridging therapy (21.4%) was significantly higher than that in the control group. Ischemic complications in the study group included chest pain suggestive of angina in one patient and acute myocardial infarction leading to death in another patient. We should pay attention to hemorrhagic complications in patients receiving heparin bridging therapy and keep in mind the possibility of lethal ischemic complications after discontinuation of antithrombotic agents.

[Successful conservative management of blunt renal rupture in a girl].

An 11-year-old girl visited the emergency room of our hospital with complaints of pain, nausea and gross hematuria after abdominal injury due to a fall from a fence. Computed tomography (CT) showed ruptured right kidney, hematoma, urinoma, and slight liver damage in S7 area. According to the Classification of Renal Injury by the Japanese Association for the Surgery of Trauma, this case was Type IIIb, but according to the American Association for the Surgery of Trauma Organ Injury Severity Scale for the Kidney, it was Type V. Because her vital signs were stable after admission, conservative management was initiated. There was no progression of anemia, and blood transfusion was not required. Right ureteral stenting was performed on the 4th hospital day because of an increase in fluid accumulation around the right kidney. Percutaneous drainage was performed on the 9th hospital day because of a further increase in fluid accumulation around the right kidney. After percutaneous drainage, fluid accumulation around the kidney was improved, and the drainage tube was removed on the 20th hospital day. The patient was discharged on the 22nd day. Although the decreased blood flow in the ruptured portion of the right kidney was observed in a subsequent CT scan, renal scintigraphy showed a relatively well maintained function of the right kidney (split renal function; right 38% and left 62%). She had no increase in blood pressure one year after renal injury.

Effects of chronic treatment with cilostazol, a phosphodiesterase 3 inhibitor, on female rat bladder in a partial bladder outlet obstruction model.

OBJECTIVE: To investigate whether bladder dysfunction after bladder outlet obstruction (BOO) could be altered by treatment with cilostazol, a phosphodiesterase 3 inhibitor (PDE3i). METHODS: Twelve-week-old female Sprague-Dawley rats were divided into 5 groups: groups 1 and 2, sham-operated rats and groups 3-5, BOO rats. Group 1 and 3 rats were given normal diet, group 2 and 5 rats were given high-dose PDE3i diet, and group 4 rats were given low-dose PDE3i diet. PDE3i was given within diet from the day of surgery. Four weeks after BOO, the bladder was excised and dissected into 4 longitudinal strips for isometric organ-bath assay. Contractile responses of bladder strips to electrical field stimulation (EFS), carbachol, and potassium chloride (KCl) were determined for each group. RESULTS: BOO induced a significant increase in bladder weight in groups 3-5 compared with groups 1 and 2. PDE3i treatment did not affect bladder weight in sham or BOO rats. Contractile forces in response to EFS, carbachol, and KCl in group 3 were about 20%-40% of those in group 1. Contractile responses to EFS or KCl in PDE3i-treated BOO rats were not significantly different from those in group 3. Only high dose of PDE3i treatment in BOO rats caused a statistically significant increase in the response to carbachol compared with group 3. CONCLUSION: PDE3i has a small but significant protective effect on the contractile dysfunction induced by a 4-week BOO in rats, although the increase in bladder mass was not altered. PDE3i could be a useful protection against contractile dysfunction of the obstructed bladder.

Bladder function in 17ß-estradiol-induced nonbacterial prostatitis model in Wistar rat.

OBJECTIVES: To investigate bladder function in a model of nonbacterial prostatitis (NBP) induced in castrated rats by 17ß-estradiol injection. METHODS: Ten-month-old male Wistar rats were divided into two groups, sham and NBP (both N = 8). NBP was induced by castration followed by daily subcutaneous injection of 17ß-estradiol for 30 days. On the 31st day after surgery, we investigated (1) voiding behavior, (2) bladder blood flow (BBF), (3) prostate and bladder weight, and proinflammatory cytokines (TNF-α and CXCL1) levels and (4) bladder contractile responses to electrical field stimulation (EFS), carbachol and KCl. RESULTS: (1) Voiding behavior (average micturition volume, total urine volume and number of micturitions) and (2) BBF were not significantly different between the sham and NBP groups. (3) NBP led to a significant decrease in prostatic weight and increase in proinflammatory cytokine levels in the prostate, but NBP did not cause a significant change in bladder weight or proinflammatory cytokine levels in the bladder. (4) Bladder contractile forces in response to EFS, carbachol and KCl were not significantly affected by NBP. CONCLUSIONS: In this rat model, NBP did not cause a significant change in the level of proinflammatory cytokines in the bladder and affect bladder function.

[Add-on effect of dutasteride in patients with benign prostatic hyperplasia treated with alpha blocker : its effect on overactive bladder].

We investigated the add-on effect of dutasteride (0.5 mg once a day) on lower urinary tract symptoms (LUTS), prostate volume (PV), and serum prostate specific antigen (PSA) and testosterone level in 72 patients with benign prostatic hyperplasia (BPH) who had been treated with alpha-blocker monotherapy. Inclusion criteria were men with BPH who had PV ≧30 ml and international prostate symptom score (IPSS) ≧8 or quality of life (QOL) index ≧3 under alpha-blocker monotherapy for more than 3 months. At the baseline, 12 and 24 weeks after dutasteride add-on, we assessed IPSS, overactive bladder symptom score (OABSS), PV, serum PSA and testosterone. Among 47 patients (65%) with OAB diagnosed by OABSS, responders were defined as those with urgency score of OABSS ＜2 or total score of OABSS ＜3. At the 24th week, dutasteride significantly improved IPSS (-4.2) and OABSS (-1.9) and reduced PV (-29%) compared with the baseline. Furthermore, dutasteride significantly decreased serum PSA (-45%) and increased testosterone (36%). Among OAB patients, dutasteride significantly improved urgency and urgency incontinence but not nocturia. Responders had lower OABSS, urgency incontinence score and serum testosterone at the baseline than non-responders. In conclusion, dutasteride add-on therapy is beneficial in patients with BPH who do not show enough improvement with alpha-blocker monotherapy.

[Solitary fibrous tumor of the adrenal gland with renal cell carcinoma and angiomyolipoma at the same time; a case report].

Solitary fibrous tumor (SFT) is a neoplasm of pleura and its occurrence in the retroperitoneal space is rare. We report a case of SFT of the adrenal gland associated with ipsilateral renal cell carcinoma (RCC) and angiomyolipoma (AML). A 48-year-old woman was referred to our hospital for a left renal AML. Computed tomography (CT) in our hospital showed a left adrenal mass (25 x 20 mm). Because the adrenal tumor was nonfunctioning, she was followed at outpatient clinic. Four years later, CT showed an increase in the left adrenal tumor size (42 x 30 mm) and a left RCC. Left adrenectomy and partial nephrectomy for RCC and AML were simultaneously performed. Histological examination revealed adrenal SFT and clear cell carcinoma and AML of the kidney. We present a brief review on histological characteristics of retroperitoneal SFT and its occurrence in the adrenal grand region.

Light-induced structural changes of the LOV2 domains in various phototropins revealed by FTIR spectroscopy.

Phototropin (Phot), a blue-light photoreceptor in plants, consists of two FMN-binding domains (named LOV1 and LOV2) and a serine/threonine (Ser/Thr) kinase domain. We have investigated light-induced structural changes of LOV domains, which lead to the activation of the kinase domain, by means of light-induced difference FTIR spectroscopy. FTIR spectroscopy revealed that the reactive cysteine is protonated in both unphotolyzed and triplet-excited states, which is difficult to detect by other methods such as X-ray crystallography. In this review, we describe the light-induced structural changes of hydrogen-bonding environment of FMN chromophore and protein backbone in Adiantum neo1-LOV2 in the C=O stretching region by use of 13C-labeled samples. We also describe the comprehensive FTIR analysis of LOV2 domains among Arabidopsis phot1, phot2, and Adiantum neo1 with and without Jα helix domain.

Key dynamics of conserved asparagine in a cryptochrome/photolyase family protein by fourier transform infrared spectroscopy.

Cryptochromes (Crys) and photolyases (Phrs) are flavoproteins that contain an identical cofactor (flavin adenine dinucleotide, FAD) within the same protein architecture but whose physiological functions are entirely different. In this study, we investigated light-induced conformational changes of a cyanobacterium Cry/Phr-like protein (SCry-DASH) with UV-visible and Fourier transform infrared (FTIR) spectroscopy. We developed a system for measuring light-induced difference spectra under the concentrated conditions. In the presence of a reducing agent, SCry-DASH showed photoreduction to the reduced form, and we identified a signal unique for an anionic form in the process. Difference FTIR spectra enabled us to assign characteristic FTIR bands to the respective redox forms of FAD. An asparagine residue, which anchors the FAD embedded within the protein, is conserved not only in the cyanobacterial protein but also in Phrs and other Crys, including the mammalian clock-related Crys. By characterizing an asparagine-to-cysteine (N392C) mutant of SCry-DASH, which mimics an insect specific Cry, we identified structural changes of the carbonyl group of this conserved asparagine upon light irradiation. We also found that the N392C mutant is stabilized in the anionic form. We did not observe a signal from protonated carboxylic acid residues during the reduction process, suggesting that the carboxylic acid moiety would not be directly involved as a proton donor to FAD in the system. These results are in contrast to plant specific Crys represented by Arabidopsis thaliana Cry1 that carry Asp at the position. We discuss potential roles for this conserved asparagine position and functional diversity in the Cry/Phr frame.

Role of Phe1010 in light-induced structural changes of the neo1-LOV2 domain of Adiantum.

Phototropin (phot) is a blue-light sensor protein that elicits several photo responses in plants. Phototropin has two flavin mononucleotide (FMN)-binding domains, LOV1 and LOV2, in its N-terminal half. The C-terminal half is a blue-light-regulated Ser/Thr kinase. Various functional studies have reported that only LOV2 is responsible for the kinase activity, whereas the X-ray crystallographic structures of the LOV1 and LOV2 domains are almost identical. How does such a functional difference emerge? Our previous FTIR study of the LOV domains of Adiantum neochrome1 (neo1) showed that light-induced protein structural changes are small and temperature independent for neo1-LOV1, whereas the structural changes are large and highly temperature dependent for neo1-LOV2, which involve loops, alpha-helices, and beta-sheets. These observations successfully explained the different functions in terms of protein structural changes. They also suggested the presence of some crucial amino acids responsible for greater protein structural changes in the LOV2 domain. Here, we focused on phenylalanine-1010 (Phe1010) in neo1-LOV2, where FMN is sandwiched between Phe1010 and the reactive cysteine. Phenylalanine at this position is conserved for LOV2 domains, while the corresponding amino acid is leucine for LOV1 domains in almost all plant phototropins. We observed that unlike wild-type LOV2, the FTIR spectra of F1010L LOV2 exhibited no temperature dependence in the alpha-helical and beta-sheet regions and that spectral changes in amide-I of these regions were significantly reduced, which was similar to LOV1. Thus, the replacement of phenylalanine with leucine converts neo1-LOV2 into neo1-LOV1 in terms of protein structural changes that must be related to the different functions. We will discuss the roles of phenylalanine and leucine in the LOV2 and LOV1 domains, respectively.

Heterogeneous environment of the S-H group of Cys966 near the flavin chromophore in the LOV2 domain of Adiantum neochrome1.

The primary photochemistry of the blue-light sensor protein, phototropin, is adduct formation between the C4a atom of the flavin mononucleotide (FMN) chromophore and a nearby, reactive cysteine (Cys966), following decay of the triplet excited state of FMN. The distance between the C4a position of FMN and the sulfur atom of Cys966 is 4.2 A in the LOV2 domain of Adiantum neochrome 1 (neo1-LOV2), a fusion protein of phototropin containing the phytochrome chromophoric domain. We previously reported the presence of an unreactive fraction in neo1-LOV2 at low temperatures, which presumably originated from the heterogeneous environment of Cys966 [Iwata, T., Nozaki, D., Tokutomi, S., Kagawa, T., Wada, M., and Kandori, H. (2003) Biochemistry 42, 8183-8191]. The present study showed that (i) 28% forms an adduct at 77 K (state I), (ii) 50% forms an adduct at 150 K but not at 77 K (state II), and (iii) 22% does not form an adduct at 150 K (state III). By Fourier transform infrared (FTIR) spectroscopy, we observed the S-H stretching frequencies at 2570 and 2562 cm-1 for state I and at 2563 cm-1 for state II, suggesting that the microenvironment of the S-H group of Cys966 determines the reactivity at low temperatures. Adduct formation is more efficient for state I than for states II and III. Molecular dynamics simulation strongly suggests that the observed multiple structures originate from the isomeric forms of Cys966. We thus concluded that there are multiple local structures of FMN and cysteine in neo1-LOV2, each of which is thermally converted by protein fluctuation at physiological temperatures.

Hydration and temperature similarly affect light-induced protein structural changes in the chromophoric domain of phototropin.

Phototropin is a blue-light sensor protein in plants, and LOV domain binds a flavin mononucleotide (FMN) as a chromophore. A photointermediate state, S390, is formed by light-induced adduct formation between FMN and an S-H group of nearby cysteine, which triggers protein structural changes for kinase activation in phototropin. We previously studied the low-temperature Fourier transform infrared (FTIR) spectra between the S390 and unphotolyzed states for a LOV2 domain of a phototropin from Adiantum (neo1-LOV2), and found that the protein structures of the S390 intermediate are highly temperature dependent (Iwata, T., Nozaki, D., Tokutomi, S., Kagawa, T., Wada, M., and Kandori, H. (2003) Biochemistry 42, 8183-8191). At physiological temperature, amide-I vibration at 1640-1620 cm-1 is significantly changed, implying structural alteration of beta-sheet region. Such changes are largely suppressed at low temperatures, though S390 is formed. This observation suggested the presence of progressive protein structural changes in the unique active state (S390). Here we report that the hydration dependence of the amide-I vibrational bands in neo1-LOV2 is similar to the temperature dependence. As hydration of the sample is lowered, amide-I vibration at 1640-1620 cm-1 is significantly reduced. Instead, amide-I vibration at 1694 cm-1 newly emerged at low hydration as well as at low temperature, which shows a weakened hydrogen bond in the loop region. Spectral coincidence between low hydrations and temperatures strongly suggested that protein structural changes are similarly restricted under such conditions. It is likely that protein fluctuations are prerequisite for formation of the active state of neo1-LOV2.

Primary processes during the light-signal transduction of phototropin.

Phototropin is a blue-light photoreceptor in plants that mediates phototropism, chloroplast relocation, stomata opening and leaf expansion. Phototropin molecule has two photoreceptive domains named LOV1 (light-oxygen-voltage) and LOV2 in the N-terminus and a serine/threonine kinase domain in the C-terminus, and acts as a blue light-regulated kinase. Each LOV domain binds a flavin mononucleotide as a chromophore and undergoes unique cyclic reactions upon blue-light absorption that comprises a cysteinyl-flavin adduct formation through a triplet-excited state and a successive adduct break to revert to the initial ground state. The molecular reactions underlying the photocycle are reviewed and one of the probable molecular schemes is presented. Adduct formation alters the secondary protein structure of the LOV domains. This structural change could be transferred to the linker between the kinase domain and involved in the photoregulation of the kinase activity. The structural changes as well as the oligomeric structures seem to differ between LOV1 and LOV2, which may explain the proposed roles of each domain in the photoregulation of the kinase activity. The photoregulation mechanism of phototropin kinase is reviewed and discussed in reference to the regulation mechanism of protein kinase A, which it resembles.

Identification of the C=O stretching vibrations of FMN and peptide backbone by 13C-labeling of the LOV2 domain of Adiantum phytochrome3.

Phototropin, a blue-light photoreceptor in plants, has two FMN-binding domains named LOV1 and LOV2. We previously observed temperature-dependent FTIR spectral changes in the C=O stretching region (amide-I vibrational region of the peptide backbone) for the LOV2 domain of Adiantum phytochrome3 (phy3-LOV2), suggesting progressive structural changes in the protein moiety (Iwata, T., Nozaki, D., Tokutomi, S., Kagawa, T., Wada, M., and Kandori, H. (2003) Biochemistry 42, 8183-8191). Because FMN also possesses two C=O groups, in this article, we aimed at assigning C=O stretching vibrations of the FMN and protein by using 13C-labeling. We assigned the C(4)=O and C(2)=O stretching vibrations of FMN by using [4,10a-13C2] and [2-13C] FMNs, respectively, whereas C=O stretching vibrations of amide-I were assigned by using 13C-labeling of protein. We found that both C(4)=O and C(2)=O stretching vibrations shift to higher frequencies upon the formation of S390 at 77-295 K, suggesting that the hydrogen bonds of the C=O groups are weakened by adduct formation. Adduct formation presumably relocates the FMN chromophore apart from its hydrogen-bonding donors. Temperature-dependent amide-I bands are unequivocally assigned by separating the chromophore bands. The hydrogen bond of the peptide backbone in the loop region is weakened upon S390 formation at low temperatures, while being strengthened at room temperature. The hydrogen bond of the peptide backbone in the alpha-helix is weakened regardless of temperature. On the other hand, structural perturbation of the beta-sheet is observed only at room temperature, where the hydrogen bond is strengthened. Light-signal transduction by phy3-LOV2 must be achieved by the progressive protein structural changes initiated by the adduct formation of the FMN.