[Clinical and etiological characteristics of infectious vulvovaginitis in children in Zhejiang province from 2009 to 2019]

Objective: To explore the clinical characteristics, common pathogens in children with vulvovaginitis. Methods: This was a retrospective cases study. A total of 3 268 children with vulvovaginitis were enrolled, who visited the Department of Pediatric and Adolescent Gynecology, Children's Hospital, Zhejiang University School of Medicine from January 2009 to December 2019. Patients were divided into 3 groups according to the age of <7, 7-<10 and 10-18 years. Patients were also divided in to 4 groups according to the season of first visit. The pathogen distribution characteristics of infective vulvovaginitis were compared between the groups. Their clinical data were collected and then analyzed by χ2 test. Results: The were 3 268 girls aged (6.2±2.5) years. There were 1 728 cases (52.9%) aged <7 years, 875 cases (26.8%) aged 7-<10 years, and 665 cases (20.3%) aged 10-18 years. Of these cases, 2 253 cases (68.9%) were bacterial vulvovaginitis, 715 cases (21.9%) were fungal vulvovaginitis and 300 cases (9.2%) were vulvovaginitis infected with other pathogens. Bacterial culture of vaginal secretions was performed in 2 287 cases, and 2 287 strains (70.0%) of pathogens were detected, of which the top 5 pathogens were Streptococcus pyogenes (745 strains, 32.6%), Haemophilus influenzae (717 strains, 31.4%), Escherichia coli (292 strains, 12.8%), Staphylococcus aureus (222 strains, 9.7%) and Klebsiella pneumoniae (67 strains, 2.9%). Regarding different age groups, H.influenzae was the most common in children under 7 years of age (40.3%, 509/1 263), S.pyogenes (41.9%, 356/849) was predominantly in children aged 7 to 10 years, and E.coli was predominant in children aged 10 to 18 years (26.3%, 46/175). Susceptibility results showed that S.pyogenes was susceptible to penicillin G (610/610, 100.0%), ceftriaxone (525/525, 100.0%), and vancomycin (610/610, 100.0%); the resistance rates to erythromycin and clindamycin were 91.9% (501/545)and 90.7% (495/546), respectively. For H.influenzae, 32.5% (161/496) produced β-elactamase, and all strains were sensitive to meropenem (489/489, 100.0%) and levofloxacin (388/388, 100.0%), while 40.5% (202/499) were resistant to ampicillin. Among E.coli, all strains were sensitive to imipenem(100%, 175/175). The resistance rates of E.coli to levofloxacin and ceftriaxone were 29.1% (43/148) and 35.1% (59/168), respectively. A total of 48 strains of methicillin-resistant Staphylococcus aureus (MRSA) were isolated with a proportion of 28.3% (45/159) in 3 268 patients. The results of drug susceptibility test showed that all MRSA strains were sensitive to linezolid 100.0% (40/40), vancomycin (45/45, 100.0%), and tigecycline (36/36, 100.0%); the resistance rates of MRSA to penicillin G, erythromycin and clindamycin were 100% (45/45), 95.6% (43/45) and 88.9% (40/45), respectively. All methicillin-sensitive Staphylococcus aureus (MSSA) strains were sensitive to oxacillin (114/114, 100.0%), linezolid (94/94, 100.0%), vancomycin (114/114, 100.0%), and tigecycline (84/84, 100.0%); it's resistance rates to penicillin G, erythromycin and clindamycin were 78.1% (89/114), 59.7% (68/114) and 46.5% (53/114), respectively. The drug resistance rate of MSSA to penicillin G, erythromycin and clindamycin were lower than those of MRSA (χ²=11.71,19.74,23.95, respectively, all P<0.001). Conclusions: The age of consultation for pediatric infectious vulvovaginitis is mainly around 6 years. The most common pathogens are S.pyogenes, H.influenzae and Escherichia coli. Third generation cephalosporins can be used as the first choice of empirical anti-infection drugs. However, the results of drug susceptibility should be considered for targeted treatment.

[Disease burden and risk factors of chronic respiratory diseases in Jiangsu Province from 1990 to 2019]

Objective: To analyze the prevalence and the trend of the disease burden of chronic respiratory diseases and relevant risk factors in Jiangsu province from 1990 to 2019 and provide evidence for the prevention and treatment of chronic respiratory diseases. Methods: The data from the 2019 Global Burden of Disease Study (GBD2019) were used to calculate the prevalence rate, mortality rate and disability-adjusted life year (DALY) rate. Software Joinpoint was used to calculate the annual percent change (APC) and average annual percent change (AAPC) of the standardized prevalence rate, standardized mortality rate and standardized DALY rate. The population attributable fractions (PAF) were used to estimate the proportion of chronic respiratory disease caused by different risk factors. Results: In 1990 and 2019, the prevalence rates of chronic respiratory diseases were 4.83% and 5.45%. The mortality rates were 134.91/100 000 and 80.99/100 000 respectively, and the DALY rates were 2 678.52/100 000 and 1 534.31/100 000 respectively. From 1990 to 2019, the age-standardized prevalence rate, mortality rate and DALY rate in Jiangsu showed a significant downward trend (AAPC values were -0.90%, -5.28% and -4.70% respectively, P<0.05). Tobacco use was the leading cause of chronic respiratory diseases, followed by air pollution, occupational exposure, suboptimal temperature and high BMI. Compared with 1990, the proportion of DALYs of chronic respiratory diseases attributable to tobacco use and high BMI increased in 2019. Conclusion: The overall burden of chronic respiratory diseases in Jiangsu shows a downward trend. Prevention and health education should be focused on the population with a smoking history and high BMI. At the same time, environmental management, attention to suboptimal temperature and control of occupational exposure factors should also be adopted as important means to prevent and control chronic respiratory diseases.

Insomnia and multiple health outcomes: umbrella review of meta-analyses of prospective cohort studies

OBJECTIVES

To evaluate existing evidence of prospective cohort studies on associations between insomnia and multiple health outcomes.

STUDY DESIGN

An umbrella review of meta-analyses of prospective cohort studies.

METHODS

A systematic search was undertaken in Pubmed, Embase, Cochrane, and Web of Science from inception to October 2021 to find meta-analyses of prospective cohort studies investigating the association of insomnia with any health outcome. The summary relative risk (SRR) for each meta-analysis was recalculated with random-effects model. The methodological quality and the quality of evidence were assessed by the A Measurement Tool to Assess Systematic Reviews and Grading of Recommendations, Assessment, Development and Evaluation, respectively.

RESULTS

A total of 25 published meta-analyses of prospective cohort studies, reporting 63 SRRs for 29 unique outcomes were included. Insomnia was mainly related to cardiovascular outcomes and mental disorders. The former comprised atrial fibrillation (SRR: 1.30, 95% confidence interval: 1.26 to 1.35), cardiovascular diseases (1.45, 1.29 to 1.64), coronary heart disease (1.28, 1.10 to 1.50), myocardial infarction (1.42, 1.17 to 1.72), and stroke (1.55, 1.39 to 1.72). The latter involved alcohol abuse (1.35, 1.08 to 1.67), all mental disorders (2.16, 1.70 to 3.97), anxiety (3.23, 1.52 to 6.85), depression (2.31, 1.90 to 2.81), suicidal ideation (2.26, 1.79 to 2.86), suicidal attempt (1.99, 1.31 to 3.02), and suicidal death (1.72, 1.42 to 2.08). Besides, insomnia enhanced the risk of Alzheimer's disease (1.51, 1.06 to 2.14) and hyperlipidemia (1.64, 1.53 to 1.76).

CONCLUSION

Insomnia exhibits considerable adverse outcomes, primarily comprises cardiovascular outcomes and mental disorders, but further studies with robustly designed trials are needed to draw firmer conclusions.

[Outcomes at discharge of preterm infants born <34 weeks' gestation]

Objective: To investigate the incidence and trend of short-term outcomes among preterm infants born <34 weeks' gestation. Methods: A secondary analysis of data from the standardized database established by a multicenter cluster-randomized controlled study "reduction of infection in neonatal intensive care units (NICU) using the evidence-based practice for improving quality (REIN-EPIQ) study". This study was conducted in 25 tertiary NICU. A total of 27 192 infants with gestational age <34 weeks at birth and admitted to NICU within the first 7 days of life from May 2015 to April 2018 were enrolled. Infants with severe congenital malformation were excluded. Descriptive analyses were used to describe the mortality and major morbidities of preterm infants by gestational age groups and different admission year groups. Cochran-Armitage test and Jonckheere-Terpstra test were used to analyze the trend of incidences of mortality and morbidities in 3 study-years. Multiple Logistic regression model was constructed to analyze the differences of outcomes in 3 study-years adjusting for confounders. Results: A total of 27 192 preterm infants were enrolled with gestational age of (31.3±2.0) weeks at birth and weight of (1 617±415) g at birth. Overall, 9.5% (2 594/27 192) of infants were discharged against medical advice, and the overall mortality rate was 10.7% (2 907/27 192). Mortality for infants who received complete care was 4.7% (1 147/24 598), and mortality or any major morbidity was 26.2% (6 452/24 598). The incidences of moderate to severe bronchopulmonary dysplasia, sepsis, severe intraventricular hemorrhage or periventricular leukomalacia, proven necrotizing enterocolitis, and severe retinopathy of prematurity were 16.0% (4 342/27 192), 11.9% (3 225/27 192), 6.8% (1 641/24 206), 3.6% (939/25 762) and 1.5% (214/13 868), respectively. There was a decreasing of the overall mortality (P<0.001) during the 3 years. Also, the incidences for sepsis and severe retinopathy of prematurity both decreased (both P<0.001). However, there were no significant differences in the major morbidity in preterm infants who received complete care during the 3-year study period (P=0.230). After adjusting for confounders, infants admitted during the third study year showed significantly lower risk of overall mortality (adjust OR=0.62, 95%CI 0.55-0.69, P<0.001), mortality or major morbidity, moderate to severe bronchopulmonary dysplasia, sepsis and severe retinopathy of prematurity, compared to those admitted in the first study year (all P<0.05). Conclusions: From 2015 to 2018, the mortality and major morbidities among preterm infants in Chinese NICU decreased, but there is still space for further efforts. Further targeted quality improvement is needed to improve the overall outcome of preterm infants.

[Clinical characteristics and antimicrobial resistance of pneumococcal infections from 9 children's hospitals in 2016]

Objective: To describe the clinical characteristics of pneumococcal infections and drug resistance of Streptococcus pneumoniae isolates from children's hospitals, which would provide reference for preventing and treating pneumococcal diseases. Methods: This was a prevalence survey. In this study, the age, specimen type, monthly distribution characteristics, and antimicrobial resistance of Streptococcus pneumoniae isolates from 9 children's hospitals in China were investigated between January 1, 2016 and December 31, 2016. The WHONET 5.6 software was used to analyze the antibiotic susceptibility of Streptococcus pneumoniae. The comparison of rates was performed by Chi-square test. Results: A total of 6 200 isolates of streptococcus pneumoniae were obtained, namely, 95.1% (5 876/6 177) from the respiratory tract specimens, 2.2% (136/6 177) from blood specimens and 0.4% (24/6 177) from cerebrospinal fluid specimens. The isolates were mainly from children older than 1 and younger than 5 years (54.7%, 3 381/6 185) . Most of strains (33.2%, 1 184/3 563) were isolated in November, December and January. Streptococcus pneumoniae isolates were completely sensitive to vancomycin (100.0%, 6 189/6 189) , linezolid (100.0%, 6 030/6 030) , moxifloxacin (100.0%, 3 064/3 064) , highly sensitive to levofloxacin (99.8%, 5 528/5 540), ertapenem (98.8%, 3 024/3 061) and lowly sensitive to erythromycin (1.7%, 102/6 016), clindamycin (3.7%, 116/3 136), and tetracycline (5%, 244/4 877), respectively. According to the parenteral susceptibility breakpoints for non-meningitis isolates, the sensitivity of Streptocococus pneumoniae to penicillin from children's hospital of Chongqing Medical University (49.3%, 892/1 809) was significantly lower than those of other hospitals (χ(2)=1 268.161, P<0.05) . Conclusions:Streptococcus pneumoniae is mainly isolated from respiratory tract, from children older than 1 and younger than 5 years and during November to January in tertiary children's hospital of China. The Streptococcus pneumoniae from children is highly sensitive to vancomycin, linezolid, moxifloxacin, levofloxacin. There are also significant differences in the sensitivity of penicillin for Streptococcus pneumoniae from different hospitals.

[Modified Chevron osteotomy combined distal soft tissue reconstruction to treat high-grade bunionette deformity]

OBJECTIVE

To explore the surgical method of using the modified chevron osteotomy combined distal soft tissue reconstruction to treat high-grade bunionette deformity.

METHODS

From June 2013 to June 2015, the modified chevron osteotomy combined distal soft tissue reconstruction was used for surgical treatment of high-grade bunionette deformity in the Department of Hand and Foot Microsurgery in Xuzhou Central Hospital.Twenty-six patients with 28 feet high-grade bunionette deformity were hospitalized for treatment, with 3 male (3 feet) and 23 female (25 feet) cases, aged 22-73 (mean 47.1) years old.The average fourth-fifth intermetatarsal angle, lateral deviation of the fifth metatarsal angle and metatarsophalangeal-fifth angle were measured on the pre-and post- operative anterior to posterior weight-beating X rays of treated feet.The American Orthopaedic Foot and Ankle Society (AOFAS) Lesser Toe Metatarsophalangeal-Interphalangeal Scale was used to evaluate the post-operative outcomes.

RESULTS

All of 26 patients were followed, with a mean 15.7 months (range 8-25 months). Primarily healing of the wound was achieved in all cases.No postoperative infection and nonunion on the osteotomy site was found during the follow-up time.The fracture healing time was 6-15 (mean 12.2) weeks.All the patients had satisfactory appearance and sensory function without callosum and metastatic metatarsalgia at the final follow-up.The post-operative fourth-fifth intermetatarsal angle, lateral deviation of the fifth metatarsal angle and metatarsophalangeal-fifth angle were significantly lesser than the pre-operative at the 6th week after operation, respectively [(5.5±1.7)°, (2.1±0.8)°, (5.7±2.6)°vs (16.4±4.2)°, (6.0±2.2)°, (10.5±7.4)°; all P<0.01]. The post-operative AOFAS score was significantly greater than the pre-operative [(87.1±6.7) vs (62.3±9.8) points, P<0.001].

CONCLUSION

The modified chevron osteotomy combined distal soft tissue reconstruction is a safe and easy treatment option for the high-grade bunionette deformity and provides patient satisfaction results.

Effects of tripeptides and lactogenic hormones on oligopeptide transporter 2 in bovine mammary gland

This study was conducted to investigate the expression of oligopeptide transporter 2 (PepT2) and its potential function in bovine mammary gland. First, the PepT2 mRNA and protein were determined in cultured mammary epithelial cells. Then the effects of lactogenic hormones (prolactin, hydrocortisone or insulin) and substrate (threonyl-phenylalanyl-phenylalanine) on PepT2 were investigated. The PepT2 mRNA and protein were successfully detected in bovine mammary epithelial cells. PepT2 gene expression was enhanced by the addition of 50, 500 and 5000 ng/ml prolactin, 10 and 100 ng/ml hydrocortisone, and 50, 500, 5000 and 50,000 ng/ml insulin. PepT2 mRNA abundance was increased when 5, 10 and 15% of threonyl-phenylalanyl-phenylalanine was included. Responses of PepT2 to lactogenic hormones and oligopeptide inferred that it may play an important role in bovine mammary gland.

The rat liver Na(+)/bile acid cotransporter. Importance of the cytoplasmic tail to function and plasma membrane targeting

To understand the potential functions of the cytoplasmic tail of Na(+)/taurocholate cotransporter (Ntcp) and to determine the basolateral sorting mechanisms for this transporter, green fluorescent protein-fused wild type and mutant rat Ntcps were constructed and the transport properties and cellular localization were assessed in transfected COS 7 and Madin-Darby canine kidney (MDCK) cells. Truncation of the 56-amino acid cytoplasmic tail demonstrates that the cytoplasmic tail of rat Ntcp is involved membrane delivery of this protein in nonpolarized and polarized cells and removal of the tail does not affect the bile acid transport function of Ntcp. Using site-directed mutagenesis, two tyrosine residues, Tyr-321 and Tyr-307, in the cytoplasmic tail of Ntcp have been identified as important for the basolateral sorting of rat Ntcp in transfected MDCK cells. Tyr-321 appears to be the major basolateral-sorting determinant, and Tyr-307 acts as a supporting determinant to ensure delivery of the transporter to the basolateral surface, especially at high levels of protein expression. When the two Tyr-based basolateral sorting motifs have been removed, the N-linked carbohydrate groups direct the tyrosine to alanine mutants to the apical surface of transfected MDCK cells. The major basolateral sorting determinant Tyr-321 is within a novel beta-turn unfavorable tetrapeptide Y(321)KAA, which has not been found in any naturally occurring basolateral sorting motifs. Two-dimensional NMR spectroscopy of a 24-mer peptide corresponding to the sequence from Tyr-307 to Thr-330 on the cytoplasmic tail of Ntcp confirms that both the Tyr-321 and Tyr-307 regions do not adopt any turn structure. Since the major motif YKAA contains a beta-turn unfavorable structure, the Ntcp basolateral sorting may not be related to the clathrin-adaptor complex pathway, as is the case for many basolateral proteins.

Solution structure of ERK2 binding domain of MAPK phosphatase MKP-3: structural insights into MKP-3 activation by ERK2

MAP kinases (MAPKs), which control mitogenic signal transduction in all eukaryotic organisms, are inactivated by dual specificity MAPK phosphatases (MKPs). MKP-3, a prototypical MKP, achieves substrate specificity through its N-terminal domain binding to the MAPK ERK2, resulting in the activation of its C-terminal phosphatase domain. The solution structure and biochemical analysis of the ERK2 binding (EB) domain of MKP-3 show that regions that are essential for ERK2 binding partly overlap with its sites that interact with the C-terminal catalytic domain, and that these interactions are functionally coupled to the active site residues of MKP-3. Our findings suggest a novel mechanism by which the EB domain binding to ERK2 is transduced to cause a conformational change of the C-terminal catalytic domain, resulting in the enzymatic activation of MKP-3.

[Changes of cerebral beta-endorphin in rats treated with combination therapy of melatonin and electroacupuncture]

OBJECTIVE

To explore the strengthening of acupuncture analgesic mechanism on the level of beta-endorphin and proopimelanocortin mRNA expression in the arcuate nucleus of hypothalamus in rats following electroacupuncture (EA) combined with melatonin (MEL).

METHODS

Integrated optical density (IOD) was measured by ABC immuno-histochemical and in situ hybridization technique with computerized image processing. The rat's brain was coronally sectioned after combination of EA and MEL.

RESULTS

IOD of beta-endorphin-like immunopositive substance in rat's brain was lowered significantly, which was measured after MEL (60 mg/kg) was injected intraperitoneally and followed by EA 30 min later for 30 min, and the IOD of cerebral POMC mRNA positive substance increased significantly 10 hrs later.

CONCLUSION

The mechanism of MEL in enhancing EA analgesic effect might be related with the release and synthesis of beta-endorphin.

Alteration of orphanin FQ immunoreactivity and ppOFQ mRNA by combination of melatonin with electroacupuncture

The aim of the present study was to observe the alternation of central orphanin FQ (OFQ, also known as nociceptin) system while electroacupuncture (EA) combined with melatonin (MEL). The experiments were carried out to investigate the changes of OFQ-like immunoreactivity and prepro-orphanin FQ (ppOFQ) mRNA in some certain nuclei of the rat brain. Using immunohistochemical technique we found that the level of OFQ-like immunoreactivity was increased significantly in some pain-modulation-related nuclei, such as ventromedial hypothalamic nucleus, raphe magnus nucleus, dorsal raphe nucleus and periaqueductal gray (PAG) after intraperitoneal (i.p.) injection of MEL 60 mg/kg, and it was further enhanced while MEL combined with EA. By using in situ hybridization, we found that ppOFQ mRNA expression was decreased in the same nuclei after the administration of MEL, and further decreased following the combination of EA and MEL. The results suggested that attenuating the release and synthesis of OFQ in the brain is one of the mechanisms that melatonin promotes acupuncture analgesia.

NMR-based discovery of phosphotyrosine mimetics that bind to the Lck SH2 domain

Using an NMR-based screen, a series of novel phosphotyrosine mimetics were discovered that bind to the SH2 domain of Lck. These compounds may serve as useful leads for the design of nonpeptide inhibitors of SH2 domains with improved bioavailability and metabolic stability compared to the natural ligands that contain phosphotyrosine.

Structure and ligand of a histone acetyltransferase bromodomain

Histone acetylation is important in chromatin remodelling and gene activation. Nearly all known histone-acetyltransferase (HAT)-associated transcriptional co-activators contain bromodomains, which are approximately 110-amino-acid modules found in many chromatin-associated proteins. Despite the wide occurrence of these bromodomains, their three-dimensional structure and binding partners remain unknown. Here we report the solution structure of the bromodomain of the HAT co-activator P/CAF (p300/CBP-associated factor). The structure reveals an unusual left-handed up-and-down four-helix bundle. In addition, we show by a combination of structural and site-directed mutagenesis studies that bromodomains can interact specifically with acetylated lysine, making them the first known protein modules to do so. The nature of the recognition of acetyl-lysine by the P/CAF bromodomain is similar to that of acetyl-CoA by histone acetyltransferase. Thus, the bromodomain is functionally linked to the HAT activity of co-activators in the regulation of gene transcription.

Phosphotyrosine binding domains of Shc and insulin receptor substrate 1 recognize the NPXpY motif in a thermodynamically distinct manner

Phosphotyrosine binding (PTB) domains of the adaptor protein Shc and insulin receptor substrate (IRS-1) interact with a distinct set of activated and tyrosine-phosphorylated cytokine and growth factor receptors and play important roles in mediating mitogenic signal transduction. By using the technique of isothermal titration calorimetry, we have studied the thermodynamics of binding of the Shc and IRS-1 PTB domains to tyrosine-phosphorylated NPXY-containing peptides derived from known receptor binding sites. The results showed that relative contributions of enthalpy and entropy to the free energy of binding are dependent on specific phosphopeptides. Binding of the Shc PTB domain to tyrosine-phosphorylated peptides from TrkA, epidermal growth factor, ErbB3, and insulin receptors is achieved via an overall entropy-driven reaction. On the other hand, recognition of the phosphopeptides of insulin and interleukin-4 receptors by the IRS-1 PTB domain is predominantly an enthalpy-driven process. Mutagenesis and amino acid substitution experiments showed that in addition to the tyrosine-phosphorylated NPXY motif, the PTB domains of Shc and IRS-1 prefer a large hydrophobic residue at pY-5 and a small hydrophobic residue at pY-1, respectively (where pY is phosphotyrosine). These results agree with the calculated solvent accessibility of these two key peptide residues in the PTB domain/peptide structures and support the notion that the PTB domains of Shc and IRS-1 employ functionally distinct mechanisms to recognize tyrosine-phosphorylated receptors.

Evidence for a requirement for both phospholipid and phosphotyrosine binding via the Shc phosphotyrosine-binding domain in vivo

The adapter protein Shc is a critical component of mitogenic signaling pathways initiated by a number of receptors. Shc can directly bind to several tyrosine-phosphorylated receptors through its phosphotyrosine-binding (PTB) domain, and a role for the PTB domain in phosphotyrosine-mediated signaling has been well documented. The structure of the Shc PTB domain demonstrated a striking homology to the structures of pleckstrin homology domains, which suggested acidic phospholipids as a second ligand for the Shc PTB domain. Here we demonstrate that Shc binding via its PTB domain to acidic phospholipids is as critical as binding to phosphotyrosine for leading to Shc phosphorylation. Through structure-based, targeted mutagenesis of the Shc PTB domain, we first identified the residues within the PTB domain critical for phospholipid binding in vitro. In vivo, the PTB domain was essential for localization of Shc to the membrane, as mutant Shc proteins that failed to interact with phospholipids in vitro also failed to localize to the membrane. We also observed that PTB domain-dependent targeting to the membrane preceded the PTB domain's interaction with the tyrosine-phosphorylated receptor and that both events were essential for tyrosine phosphorylation of Shc following receptor activation. Thus, Shc, through its interaction with two different ligands, is able to accomplish both membrane localization and binding to the activated receptor via a single PTB domain.

Changes in the NMR-derived motional parameters of the insulin receptor substrate 1 phosphotyrosine binding domain upon binding to an interleukin 4 receptor phosphopeptide

Proteins recognize ligands by forming specific intermolecular interactions that often involve solvent exposed residues. Changes in the motional properties of these residues upon binding can affect the conformational entropy of the system and thus are related to the energetics of binding. The role that dynamics plays in ligand recognition can be investigated by comparing the motional properties of a free and ligated protein. NMR relaxation studies are well suited for examining changes in dynamics, especially for motions on a nanosecond to picosecond time scale. Recently, we determined the solution structure of the phosphotyrosine binding (PTB) domain of the insulin receptor substrate (IRS-1) complexed to a tyrosine-phosphorylated peptide derived from the interleukin 4 (IL-4) receptor [Zhou et al., (1996) Nat. Struct. Biol. 3, 388-393]. The peptide binds tightly to the protein in a surface exposed pocket, resulting in the partial burial of many protein residues. Using NMR relaxation studies, the dynamics of the backbone nitrogens of IRS-1 PTB domain were studied in both the free protein and the protein when complexed to the IL-4 receptor phosphopeptide. The backbone nitrogens of many residues that make important contacts to the ligand are motionally restricted in the free and complexed protein. Additional residues become motionally restricted only after ligand binding, including several residues that do not make any direct contacts with the ligand. These observed changes in the dynamics are compared to structural features of the complex.

Structural basis for IL-4 receptor phosphopeptide recognition by the IRS-1 PTB domain

We present the NMR structure of the PTB domain of insulin receptor substrate-1 (IRS-1) complexed to a tyrosine-phosphorylated peptide derived from the IL-4 receptor. Despite the lack of sequence homology and different binding specificity, the overall fold of the protein is similar to that of the Shc PTB domain and closely resembles that of PH domains. However, the PTB domain of IRS-1 is smaller than that of Shc (110 versus 170 residues) and binds to phosphopeptides in a distinct manner. We explain the phosphopeptide binding specificity based on the structure of the complex and results of site-directed mutagenesis experiments.

Binding affinities of tyrosine-phosphorylated peptides to the COOH-terminal SH2 and NH2-terminal phosphotyrosine binding domains of Shc

The adaptor protein Shc has been implicated in Ras signaling via association with many tyrosine-phosphorylated receptors, including growth factor receptors, antigen receptors on T and B cells, and cytokine receptors. Shc could interact with the activated receptors through the carboxyl-terminal Src homology 2 (SH2) domain or the structurally unrelated amino-terminal phosphotyrosine binding (PTB) domain. Using NMR and surface plasmon resonance techniques, we have measured the binding affinities of the SH2 and the PTB domains of Shc to a series of phosphotyrosine-containing peptides derived from known Shc binding sites. Tyrosine-phosphorylated peptides derived from Trk (pY490), polyoma virus middle T-antigen (pY250), ErbB3 (pY1309), and epidermal growth factor receptor (pY1086, pY1148, and pY1114) that contain NPXpY sequences bind preferentially to the PTB domain of Shc with Kd values of 0.02-5.3 microM. The binding affinities of these peptides to the Shc SH2 domain were in the range of 220-1290 microM. In contrast, tyrosine-phosphorylated peptides from epidermal growth factor receptor (pY992, pY1173) and the zeta chain of the T-cell receptor bind preferentially to the SH2 domain (Kd = 50-130 microM) versus the PTB domain (Kd > 680 microM). From these studies, the relative contribution of the individual domains of Shc for binding to the phosphotyrosine-containing portions of these proteins was determined. In addition, our data indicate that the high affinity binding of the PTB domain to the NPXpY-containing peptides results from a very high association rate and a rapid dissociation rate, which is similar to previous results observed for the SH2-phosphopeptide complexes.

Structure and ligand recognition of the phosphotyrosine binding domain of Shc

The nuclear magnetic resonance structure of the phosphotyrosine binding (PTB) domain of Shc complexed to a phosphopeptide reveals an alternative means of recognizing tyrosine-phosphorylated proteins. Unlike in SH2 domains, the phosphopeptide forms an antiparallel beta-strand with a beta-sheet of the protein, interacts with a hydrophobic pocket through the (pY-5) residue, and adopts a beta-turn. The PTB domain is structurally similar to pleckstrin homology domains (a beta-sandwich capped by an alpha-helix) and binds to acidic phospholipids, suggesting a possible role in membrane localization.

Solution structure of the Shc SH2 domain complexed with a tyrosine-phosphorylated peptide from the T-cell receptor

She is a widely expressed adapter protein that plays an important role in signaling via a variety of cell surface receptors and has been implicated in coupling the stimulation of growth factor, cytokine, and antigen receptors to the Ras signaling pathway. She interacts with several tyrosine-phosphorylated receptors through its C-terminal SH2 domain, and one of the mechanisms of T-cell receptor-mediated Ras activation involves the interaction of the Shc SH2 domain with the tyrosine-phosphorylated zeta chain of the T-cell receptor. Here we describe a high-resolution NMR structure of the Shc SH2 domain complexed to a phosphopeptide (GHDGLpYQGLSTATK) corresponding to a portion of the zeta chain of the T-cell receptor. Although the overall architecture of the protein is similar to other SH2 domains, distinct structural differences were observed in the smaller beta-sheet, BG loop, (pY + 3) phosphopeptide-binding site, and relative position of the bound phosphopeptide.

Solution structure of a low molecular weight protein tyrosine phosphatase

Protein tyrosine phosphatases (PTPs) are important enzymes involved in signal transduction, cell cycle regulation, and the control of differentiation. Despite the importance of this class of enzymes in the control of critical cell processes, very little structural information is available for this family of proteins. In this paper, we present the first solution structure of a protein tyrosine phosphatase. This protein is a low molecular weight cytosolic PTP that was initially isolated from bovine heart. The structure that was determined from 1747 NMR-derived restraints consists of a central four-stranded parallel beta-sheet surrounded by four alpha-helices and a short 3(10) helix. The phosphate binding site, identified by chemical shift changes upon the addition of the competitive inhibitors phosphate and vanadate, is in a loop region connecting the C-terminal end of the first beta-strand with the first alpha-helix. Residues in the second, fourth, and fifth alpha-helices and in some of the loop regions connecting the elements of regular secondary structure also contribute to the binding site. The structure determined here is consistent with previous mutagenesis and chemical modification studies conducted on this protein.

Backbone 1H, 13C, and 15N assignments and secondary structure of bovine low molecular weight phosphotyrosyl protein phosphatase

Phosphotyrosyl protein phosphatases play an important role in mediating cellular signal transduction; yet three-dimensional structures of this important class of proteins have not been reported. We present the sequence-specific 1H, 13C, and 15N backbone assignments for the low molecular weight bovine heart phosphotyrosyl protein phosphatase (BHPTPase) (157 residues, 17,900). The assignments were obtained from a combination of double- and triple-resonance multidimensional NMR experiments. From these assignments, the secondary structure of BHPTPase was determined from an analysis of NOE patterns, 3JHNH alpha coupling constants, 13C alpha and 13CO chemical shifts, and amide 1H exchange rates. BHPTPase was found to consist of a four-stranded parallel beta-sheet (residues K6-C12, W39-A45, Y87-M91, and K112-L116), four alpha-helices (residues I21-D32, R58-G67, S94-N104, and D135-R157), and one stretch of beta 10-helix (residues K79-F85). The secondary structure is characteristic of the beta alpha beta structural motif. The secondary structure elements identified in this study are consistent with previous chemical and mutagenesis studies of BHPTPase structure.

Kinetic and site-directed mutagenesis studies of the cysteine residues of bovine low molecular weight phosphotyrosyl protein phosphatase

The roles of the 8 conserved cysteines and 1 arginine in the low molecular weight phosphotyrosyl protein phosphatases were investigated using site-directed mutagenesis of the recombinant bovine heart enzyme. Single mutants of cysteine to serine were studied for each cysteine; alanine replacements were also made for Cys-12, Cys-17, and Arg-18. The CD spectra of the purified proteins were effectively superimposable, consistent with the conclusion that no major structural alterations had occurred, but 1H NMR spectroscopy did reveal some spectral shifts in the aromatic region. Kinetic analysis of the mutant proteins demonstrated that only Cys-12, Cys-17, and Arg-18 had significantly altered catalytic activity toward the substrate p-nitrophenyl phosphate at pH 5. The Cys-12 and Arg-18 mutants were effectively inactive. Thus, it is concluded that Cys-12 is the catalytic nucleophile, and Arg-18 presumably serves an essential function in substrate binding. The C17S mutant had 6% residual activity compared with wild type protein, whereas the C17A mutant had 37% activity. Consistent with the observed activity of the Cys-17 mutant, a covalent phosphocysteine intermediate was trapped and identified by 31P NMR. Further kinetic analysis of C17A using several aryl phosphate monoester substrates with different leaving group pK alpha values indicated that no change in the rate-determining step of the catalytic mechanism had occurred, that is, dephosphorylation of the covalent phosphoenzyme intermediate remains rate-limiting. The C17A mutant had a 4-fold higher phosphate Ki and slightly higher Km values for p-nitrophenyl phosphate suggesting that Cys-17 may be important for optimal positioning of the substrate phosphate moiety.

Spectroscopic and kinetic studies of the histidine residues of bovine low-molecular-weight phosphotyrosyl protein phosphatase

The role of the two conserved histidine residues in the low-molecular-weight phosphotyrosyl protein phosphatases was investigated using site-directed mutagenesis of the recombinant bovine heart enzyme. His-66 and His-72 were individually mutated to alanine and to asparagine. A double mutant, containing only alanines in place of the histidines, was also created. The 1H NMR spectra of the purified proteins revealed no apparent tertiary structure alterations. Microscopic pKas for the two histidines were determined from a pH titration of the wild-type enzyme using 1H NMR spectroscopy and an MLEV-17 spectral editing scheme to more readily follow shifts in the specific histidine resonance peaks. His-66 titrates with an apparent pKa of 8.4 while for His-72 the value is 9.2. Since earlier chemical modification experiments indicated that the wild-type enzyme was inactivated by the histidine-selective modification reagent diethyl pyrocarbonate (DEP), the histidine mutants were tested for sensitivity to DEP. Both of the histidine single mutants were inactivated by DEP, and surprisingly, the double mutant containing no histidines was also readily inactivated by DEP. Thus, for this protein, modification by DEP is not specific for histidine residues. Kinetic studies of the mutant proteins reveal that neither histidine is essential in the catalytic mechanism. His-66 mutants showed virtually identical catalytic properties compared to wild-type enzyme, whereas His-72 mutants had reduced specific activity and higher phosphate Ki and lower Km values at pH5 and higher. It is proposed that His-72, although not essential for catalysis, may serve a significant structural role at the enzyme active site.

Identification and pKa determination of the histidine residues of human low-molecular-weight phosphotyrosyl protein phosphatases: a convenient approach using an MLEV-17 spectral editing scheme

A useful approach using an MLEV-17 pulse sequence was developed to identify histidine C epsilon 1H magnetic resonances of proteins. This technique can be readily applied to proteins dissolved directly in deuterium oxide solution and eliminates the necessity for an exhaustive exchange of NH to ND. Because of its sensitivity, this technique makes it possible to significantly extend the limitations on protein size. The utility of this spin-lock sequence is demonstrated using ribonuclease, subtilisin, and human prostatic acid phosphatase, with molecular weights ranging from 12K to 100K. With this technique, all three or four of the histidine 1H NMR signals of two human low-molecular-weight phosphotyrosyl protein phosphatases (HCPTP-A or -B, respectively) were readily detected. Histidine peak assignments were accomplished through the use of histidine to alanine mutants of HCPTP-A and -B and a homologous bovine enzyme. Analysis of the pH titration curves of these signals provided microscopic pKa's for the histidines in the human enzymes. A comparison of corresponding histidine pKa values of the two isoenzymes, together with an examination of the 1H NMR spectra of the proteins, provided evidence of significant differences in secondary structure. Titration of HCPTP-A and -B with vanadate, a strongly bound competitive inhibitor, caused the His-72 peak to appear as two signals at nearly equimolar concentrations of protein and vanadate, while the other histidine peaks were not affected. This is interpreted to mean that His-72 is at the enzyme active site.

Overexpression, site-directed mutagenesis, and mechanism of Escherichia coli acid phosphatase

Site-directed mutagenesis was used to examine the catalytic importance of 2 histidine and 4 arginine residues in Escherichia coli periplasmic acid phosphatase (EcAP). The residues that were selected as targets for mutagenesis were those that were also conserved in a number of high molecular weight acid phosphatases from eukaryotic organisms, including human prostatic and lysosomal acid phosphatases. Both wild type EcAP and mutant proteins were overproduced in E. coli using an expression system based on the T7 RNA polymerase promoter, and the proteins were purified to homogeneity. Examination of the purified mutant proteins by circular dichroism and proton NMR spectroscopy revealed no significant conformational changes. The replacement of Arg16 and His17 residues that were localized in a conserved N-terminal RHGXRXP motif resulted in the complete elimination of EcAP enzymatic activity. Critical roles for Arg20, Arg92, and His303 were also established because the corresponding mutant proteins exhibited residual activities that were not higher than 0.4% of that of wild type enzyme. In contrast, the replacement of Arg63 did not cause a significant alteration of the kinetic parameters. The results are in agreement with a previously postulated distant relationship between acid phosphatases, phosphoglycerate mutases, and fructose-2,6-bisphosphatase. These and earlier results are also consistent with the conclusion that 2 histidine residues participate in the catalytic mechanism of acid phosphatases, with His17 playing the role of a nucleophilic acceptor of the phospho group, whereas His303 may act as a proton donor to the alcohol or phenol.

Cloning, expression, and catalytic mechanism of the low molecular weight phosphotyrosyl protein phosphatase from bovine heart

The first representative of a group of mammalian, low molecular weight phosphotyrosyl protein phosphatases was cloned, sequenced and expressed in Escherichia coli. Using a 61-mer oligonucleotide probe based on the amino acid sequence of the purified enzyme, several overlapping cDNA clones were isolated from a bovine heart cDNA library. A full-length clone was obtained consisting of a 27-bp 5' noncoding region, an open reading frame encoding the expected 157 amino acid protein, and an extensive 3' nontranslated sequence. The identification of the clone as full length was consistent with results obtained in mRNA blotting experiments using poly(A)+ mRNA from bovine heart. The coding sequence was placed downstream of a bacteriophage T7 promoter, and protein was expressed in E. coli. The expressed enzyme was soluble, and catalytically active and was readily isolated and purified. The recombinant protein had the expected Mr of 18,000 (estimated by SDS-PAGE), and it showed cross-reactivity with antisera that had been raised against both the bovine heart and the human placenta enzymes. The amino acid sequence of the N-terminal region of the expressed protein showed that methionine had been removed, resulting in a sequence identical to that of the enzyme isolated from the bovine tissue, with the exception that the N-terminal alanine of the protein from tissue is acetylated. A kinetically competent phosphoenzyme intermediate was trapped from a phosphatase-catalyzed reaction. Using 31P NMR, the covalent intermediate was identified as a cysteinyl phosphate. By analogy with the nomenclature used for serine esterases, these enzymes may be called cysteine phosphatases.