Characterisation of variant forms of prophenin: mechanistic aspects of the fragmentation of proline-rich peptides

Prophenin 1 (PF-1) is a 79-residue polypeptide originally isolated from porcine leukocytes. Its amino acid sequence has been determined by a combination of mass spectrometry and Edman degradation (Harwig SSL. et al. FEBS Lett. 1995; 362: 65). Prophenin (PF) and variants thereof are also found in organic extracts of porcine pulmonary tissue (Wang Y. et al. FEBS Lett. 1999; 460: 257). In the present study we have characterised the variant forms of PF found in these extracts using nano-electrospray (nano-ES) high resolution and tandem mass spectrometry. The major forms of PF found in these extracts by nano-ES mass spectrometry are the 80-residue polypeptides prophenin-2-Pyr (PF-2-Pyr) and prophenin-2-Gln (PF-2-Gln). Prophenin-2-Pyr is refractory to Edman degradation due to the presence of an N-terminal pyroglutamic residue. In PF-2-Gln the N-terminal residue is glutamine and the C-terminus is amidated. In porcine pulmonary extracts PF-1 is present to only a minor extent. Other shorter polypeptides are also found in these extracts including 18- and 17-residue C-terminal fragments of PF. The primary structure of PF is highly unusual in that it shows four almost perfect decamer repeats of FPPPN(V/F)PGPR and, out of the 79/80 residues, 42 are proline and 14 are phenylalanine. Tryptic digestion of PF gives peptides containing the decamer repeat and collision-induced dissociation of these peptides provides an insight into the fragmentation mechanisms of proline-rich peptides. Facile cleavage within the Pro-Pro-Pro sequence of these peptides suggests the involvement of a cyclic peptide in the fragmentation mechanism. Fragmentation mechanisms that account for the formation of fragment ions at other cleavage sites are also discussed.

Suppression of gastric acid secretion in patients with gastroesophageal reflux disease results in gastric bacterial overgrowth and deconjugation of bile acids

The aim of this study was to test the hypothesis that gastric bacterial overgrowth is a side effect of acid suppression therapy in patients with gastroesophageal reflux disease (GERD) and that the bacteria-contaminated gastric milieu is responsible for an increased amount of deconjugated bile acids. Thirty patients with GERD who were treated with 40 mg of omeprazole for at least 3 months and 10 patients with GERD who were off medication for at least 2 weeks were studied. At the time of upper endoscopy, 10 ml of gastric fluid was aspirated and analyzed for bacterial growth and bile acids. Bacterial overgrowth was defined by the presence of more than 1000 bacteria/ml. Bile acids were quantified via high-performance liquid chromatography. Eleven of the 30 patients taking omeprazole had bacterial overgrowth compared to one of the 10 control patients. The median pH in the bacteria-positive patients was 5.3 compared to 2.6 in those who were free of bacteria and 3.5 in the control patients who were off medication. Bacterial overgrowth only occurred when the pH was >3.8. The ratio of conjugated to unconjugated bile acids changed from 4:1 in the patients without bacterial overgrowth to 1:3 in those with bacterial growth greater than 1000/ml. Proton pump inhibitor therapy in patients with GERD results in a high prevalence of gastric bacterial overgrowth. The presence of bacterial overgrowth markedly increases the concentration of unconjugated bile acids. These findings may have implications in the pathophysiology of gastroesophageal mucosal injury.

Amyloid fibril formation by pulmonary surfactant protein C

Lung surfactant protein C (SP-C) is a lipopeptide that contains two fatty acyl (palmitoyl) chains bound via intrinsically labile thioester bonds. SP-C can transform from a monomeric alpha-helix into beta-sheet aggregates, reminiscent of structural changes that are supposed to occur in amyloid fibril formation. SP-C is here shown to form amyloid upon incubation in solution. Furthermore, one patient with pulmonary alveolar proteinosis (PAP, a rare disease where lung surfactant proteins and lipids accumulate in the airspaces) and six healthy controls have been studied regarding presence and composition of amyloid fibrils in the cell-free fraction of bronchoalveolar lavage (BAL) fluid. Abundant amyloid fibrils were found in BAL fluid from the patient with PAP and, in low amounts, in three of the six healthy controls. SDS-insoluble fibrillar material associated with PAP mainly consists of SP-C, in contrast to the fibrils found in controls. Fibrillated SP-C has to a significant extent lost the palmitoyl groups, and removal of the palmitoyl groups in vitro increases the rate of fibril formation.

Endoscopic grading of the gastroesophageal valve in patients with symptoms of gastroesophageal reflux disease (GERD)

BACKGROUND

It has been suggested that endoscopic grading of the gastroesophageal flap valve is a good predictor of the reflux status.

METHODS

To test this hypothesis, 268 symptomatic patients underwent endoscopic grading of the gastroesophageal valve using Hill's classification, with grades I through IV. Esophageal acid exposure, lower esophageal sphincter characteristics, and the degree of esophageal mucosal injury were compared among the groups.

RESULTS

The prevalence of a mechanically defective sphincter, abnormal esophageal acid exposure, erosive esophagitis, and Barrett's esophagus increased with increasing alteration of the gastroesophageal valve. The presence of a grade IV valve indicated increased esophageal acid exposure in 75% of patients. As a predictor, this is similar to lower esophageal sphincter pressure but not as good as the presence of esophageal mucosal injury.

CONCLUSIONS

Endoscopic grading of the gastroesophageal valve provides useful information about the reflux status but is less useful as an indicator of gastroesophageal reflux disease (GERD) than the presence of esophageal mucosal injury.

Pharyngeal reflux after gastric pull-up esophagectomy with neck and chest anastomoses

OBJECTIVE

Pharyngeal reflux after a gastric pull-up esophagectomy may cause aspiration. This study evaluates acid exposure to the esophageal remnant and to the pharynx after gastric pull-up esophagectomy and evaluates the impact of additional dissection of the esophagus that is necessary for neck anastomoses versus no neck exploration and proximal chest anastomoses.

METHODS

Forty-seven patients had circular stapled anastomoses in the apex of the right chest (n = 27 patients) or manually sutured neck anastomoses (n = 20 patients). A 24-hour double-pH study with the probes placed 3 cm cranial and 3 cm distal to the cricopharyngeal muscle was performed. The percent time pH less than 4 was registered 3, 6, and 12 months after the operation.

RESULTS

Mean acid exposure to the proximal pH probe ranged between 0.2% and 0.96% and between 1.45% and 6.5% to the distal pH probe during the 3 measurements. Acid exposure was always lower to the proximal than to the distal probe (P =.001). Patients with neck anastomoses had increasing acid exposure to the distal (P =.023) and proximal (P =.002) pH probes during the study year, whereas patients with chest anastomoses had similar acid exposure.

CONCLUSIONS

Acid exposure to the esophageal remnant and to the pharynx increased during the first postoperative year in patients with neck anastomoses but not in patients with proximal chest anastomoses. The results suggest a less favorable acid clearance in patients with the neck approach.

Isolation and characterization of hydrophobic polypeptides in human bile

Polypeptides were isolated from human bile by extraction with chloroform/methanol, followed by reversed-phase chromatography in methanol/ethylene chloride and gel filtration in chloroform/methanol. Peptides were characterized by SDS/PAGE, sequence analysis and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry. This identified haemoglobin alpha chain, ATP synthase lipid-binding protein subunit 9, an N-terminal fragment of mac25/insulin-like growth factor-binding protein 7 and an internal fragment of monocyte differentiation antigen CD14, all not described previously in bile. In addition, alpha1-antitrypsin, known in bile from previous work, was also identified. The hydrophobic character of haemoglobin alpha chain is not apparent from its amino acid sequence, but the other polypeptides all have major hydrophobic segments. These results show that several proteins are removed upon organic solvent extraction used for delipidation during the preparation of samples for proteome analysis. Several of the polypeptides found are unexpectedly present in bile, suggesting that specific excretion mechanisms may be involved.

A method for S- and O-palmitoylation of peptides: synthesis of pulmonary surfactant protein-C models

A method for O- and S-palmitoylation of non-protected peptides has been developed. The peptides are treated with excess of palmitoyl chloride in 100% trifluoroacetic acid for 10 min at room temperature. The acidic conditions prevent acylation of amino groups, which is only significant after prolonged treatment (hours to days). The tripeptides Gly-Cys-Phe and Gly-Ser-Phe were converted into the respective S- and O-palmitoylated compounds, and the hydrophobic pulmonary surfactant protein-C model peptides, LRIPCCPVNLKRLLVVV [SP-C(1-17)] and FGIPSSPVLKRLLILLLLLLLILLLILGALLMGL [SP-C(Leu)] were converted into their respective S,S- and O,O-dipalmitoylated peptides. The reactions were virtually quantitative, and the palmitoylated peptides were isolated in about 75-80% yield after reversed-phase HPLC purification. CD spectroscopy showed that S, S-dipalmitoylation of SP-C(1-17) affects the peptide secondary structure (substantial increase in the alpha-helix content) in dodecylphosphocholine micelles.

Porcine pulmonary surfactant preparations contain the antibacterial peptide prophenin and a C-terminal 18-residue fragment thereof

Surfactant preparations obtained from porcine lungs by extraction with chloroform/methanol followed by chromatography over Lipidex-5000 are used for treatment of respiratory distress syndrome in preterm infants. These preparations contain about 98% phospholipids and 1-2% of the hydrophobic pulmonary surfactant-associated proteins B and C (SP-B and SP-C). Separation of the proteins in the surfactant preparation by reversed-phase high performance liquid chromatography revealed, in addition to SP-B and SP-C, the presence of three peptides derived from the cathelicidin family of antibacterial peptides. The 79-residue proline-rich peptide prophenin (identical to that isolated from leukocytes), an 80-residue prophenin with an N-terminal pyroglutamic acid residue, and a C-terminal 18-residue fragment of prophenin were found in approximate molar ratios of 1:20:5. A synthetic version of the C-terminal 18-residue peptide exhibits salt-dependent antibacterial activity (higher activity in the absence of salt) against the Gram-positive bacterium Bacillus megaterium Bm11 and, to a lesser extent, against Gram-negative Escherichia coli D21 cells. It appears possible that the presence of prophenin peptides may contribute to the antibacterial properties of surfactant preparations.

Differential protease-mediated turnover of H-NS and StpA revealed by a mutation altering protein stability and stationary-phase survival of Escherichia coli

The Escherichia coli proteins H-NS is recognized as an important component among the major nucleoid-associated proteins. In studies of E. coli strains with defects in H-NS, we discovered a mutant that phenotypically restored stationary-phase viability (Rsv) of such strains. The Rsv phenotype was the result of a mutation that led to severalfold higher levels of the functionally and structurally related StpA protein. This mutation was a base pair change in the stpA structural gene, and the amino acid substitution in the StpA protein altered its turnover properties, suggesting a role for this residue in a cleavage site for proteolysis. We determined the stability of the StpA and the H-NS proteins and found that the StpA protein was degraded relatively rapidly in strains lacking functional H-NS, whereas H-NS remained stable irrespective of the presence/absence of StpA. Using protease-deficient mutants, we obtained evidence that the Lon protease was responsible for the degradation of StpA. The differential turnover of the nucleoid-associated proteins is suggested to contribute to the regulation of their stoichiometry and ratio in terms of homo- and heteromer formation. We conclude that StpA, in contrast to H-NS, is present mainly in heteromeric form in E. coli.

Carotid artery diameter correlates with risk factors for cardiovascular disease in a population of 55-year-old subjects

BACKGROUND AND PURPOSE

We investigated whether, in a randomly selected population of 55-year-old men and women, there is a relationship between common carotid artery (CCA) diameter and intima-media (IM) thickness and conventional risk factors for cardiovascular disease such as gender, smoking, elevated blood lipids, and high blood pressure.

METHODS

CCA diameter and IM thickness of the distal right and left CCAs were measured by high-frequency ultrasound methods. Fifty-seven men (73% of the invited men) and 47 women (62% of the invited women) participated.

RESULTS

In the whole group the CCA diameter was correlated with gender (P<0.001), cholesterol (P=0.007), triglycerides (P<0.001), apoB (P<0.001), apoB/A-1 (P<0.001), systolic blood pressure (P=0. 001), and glucose (P=0.006). HDL was inversely correlated with mean CCA diameter (P=0.003). In men the CCA diameter was correlated with a combined risk factor score (P=0.005), systolic blood pressure (P=0. 011), platelet count (P=0.033), apoB (P=0.025), and occurrence of plaque (P=0.003). In women the CCA diameter was correlated with a combined risk factor score (P=0.010), systolic blood pressure (P=0. 033), body mass index (P<0.001), cholesterol (P=0.009), triglycerides (P=0.14), apoB (P=0.002), and apoB/A1 (P=0.003). IM thickness was correlated with systolic blood pressure (P<0.001).

CONCLUSIONS

There are correlations between risk factors for cardiovascular disease and carotid artery diameter and IM thickness in both women and men in a population of 55-year-old subjects. The increased vessel diameter in subjects with cardiovascular risk factors may be a sign of attenuated vasoregulation, which could be an important factor during the development of atherosclerosis.

Four years experience of a cardiovascular opportunistic screening and prevention programme in the primary health care in Sollentuna, Sweden

OBJECTIVE

To study the feasibility of a cardiovascular prevention programme.

DESIGN

Opportunistic screening for cardiovascular risk factors. Advice and treatment to reduce identified cardiovascular risk factors. Individually designed follow-up.

SETTING

Primary health care in Sollentuna (51,000 inhabitants), Sweden.

SUBJECTS

Visitors to health care centres.

MAIN OUTCOME MEASURES

Feasibility and effectiveness to reduce identified cardiovascular risk factors.

RESULTS

During 4 years 5622 persons, of whom 4655 (83%) were in the age group 20-60 years, participated in the programme. The prevalences of risk factors as smoking, overweight, hypertension, hypercholesterolaemia and hypertriglyceridaemia were high. At follow-up investigations, mean S-cholesterol levels were reduced by 7% among men and 10% among women. S-triglycerides were reduced by 24% and 42%, respectively. Diastolic blood pressures were reduced in men from 95 to 90 mmHg and in women from 94 to 88 mmHg. However, no effects on weight were noted and due to a low follow-up rate meaningful analysis of smoking habits was not possible.

CONCLUSION

A programme for cardiovascular screening and prevention can be integrated in the primary health care system. Prevalent cardiovascular risk factors like hypercholesterolaemia, hypertriglyceridaemia and high blood pressure were significantly reduced after intervention.

Is there a relationship between balance, gait performance and muscular strength in 75-year-old women?

OBJECTIVE

To see if there is a relationship between clinical and laboratory tests of balance, muscular strength and gait in elderly women.

DESIGN

A randomized population-based study.

SETTINGS

Malmö, Sweden.

METHODS

We investigated balance with a simple test of standing on one leg, as well as a computerized balance platform. Muscular strength was tested by computerized dynamometer. Extension and flexion of the knee and dorsiflexion of the ankle were tested. We measured the time and number of steps taken to walk a certain distance and the subjects' height and weight.

PARTICIPANTS

418 randomly selected 75-year-old women, of whom 230 took part.

RESULTS

There was no relation between the computerized balance tests and any of the other tests. The non-computerized balance test was correlated with gait time and number of steps (r = -0.50, P<0.001 and r = -0.40, P<0.001, respectively). Tests of extension and flexion, strength of the knee and ankle dorsiflexion were related to gait, speed and number of steps. Heavy women had poorer balance when assessed by the non-computerized test (r = -0.32, P<0.001) and with the computerized, stable platform, eyes-open test (r = 0.27, P<0.001) and eyes-closed test (r = 0.44, P<0.001). The heavier an individual was, the slower her gait and the shorter her steps, despite having stronger knee muscles.

CONCLUSION

There is no relationship between the simple balance tests and computerized platform tests. Muscle strength of the leg is not necessarily linked to balance, but rather to gait performance.

Self-report as a selection instrument in screening for cardiovascular disease risk

INTRODUCTION

Cardiovascular disease (CVD) risk screening may rely partly on self-report information. The accuracy of self-reporting in relation to the actual risk factor status is insufficiently known.

DESIGN

Self-report (yes, no, don't know) of presence of hypertension, hyperlipidemia, and overweight was compared to the corresponding risk factor data obtained by physical examination and blood analysis. The examinations carried out in a primary health care setting in Sweden were on a randomized population of 122 men and 127 women aged 20 to 60 years.

RESULTS

Unawareness of hyperlipidemia was 71% in women and 56% in men, as compared to 29% or lower for the other risk factors. The sensitivity of self-report was 69% or higher for the other risk factors, with the exception of hypertension in women, where it was 29%. Specificity was generally high, except for hyperlipidemia.

CONCLUSION

On a population level, self-reports of hypertension, hyperlipidemia, and overweight provide a feasible selection instrument by which a subpopulation with high risk factor frequency can be identified. However, the rate of misclassification is considerable. For hyperlipidemia, the benefit of self-reporting is presently limited, due to the high unawareness of this risk factor. Individual awareness and accurate knowledge about the presence or absence of risk factors needs to improve before self-reporting can be used as a reliable instrument in risk factor screening.

Alterations in protein expression caused by the hha mutation in Escherichia coli: influence of growth medium osmolarity

The Hha protein belongs to a new family of regulators involved in the environmental regulation of virulence factors. The aim of this work was to study the effect of the hha mutation on the overall protein pattern of Escherichia coli cells by two-dimensional polyacrylamide gel electrophoresis. The growth medium osmolarity clearly influenced the effect of the hha mutation. The number of proteins whose expression was altered in hha cells, compared with wild-type cells, was three times larger at a high osmolarity than at a low osmolarity. Among the proteins whose expression was modified by the hha allele, both OmpA and protein IIAGlc of the phosphotransferase system could be identified. As this latter enzyme participates in the regulation of the synthesis of cyclic AMP and hence influences the catabolite repression system, we tested whether the expression of the lacZ gene was also modified in hha mutants. This was the case, suggesting that at least some of the pleiotropic effects of the hha mutation could be caused by its effect on the catabolite repression system.

Biophysical activity of an artificial surfactant containing an analogue of surfactant protein (SP)-C and native SP-B

Natural surfactant preparations containing phospholipids and the hydrophobic surfactant proteins B and C (SP-B and SP-C) are effective in the treatment of respiratory distress syndrome in premature infants. The limited supply, and the risk of infectious agents and immunological reactions have promoted the evaluation of synthetic peptides in surfactant preparations. However, the folding of synthetic SP-C into an alpha-helix is inefficient and alpha-helical SP-C analogues with Val-->Leu substitutions form oligomers. In order to circumvent these problems we have synthesized an SP-C analogue, named SP-C(LKS), which differs from SP-C mainly by the exchange of most of the Val residues in positions 16-28 with Leu residues to promote an alpha-helical conformation, and by the introduction of Lys residues at positions 17, 22 and 27 in order to locate positive charges around the helical circumference and thereby avoid self polymerization. CD spectroscopy showed a spectrum typical for alpha-helical peptides and SDS/PAGE disclosed a single band. The biophysical activity of artificial surfactant preparations containing SP-C(LKS) and phospholipids, with and without native SP-B, was measured using a Wilhelmy balance and a pulsating bubble surfactometer. SP-C(LKS) (3%, w/w) in a mixture of 1, 2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)/phosphatidylglycerol/palmitic acid (68:22:9, by wt.) suspended in 150 mM NaCl, showed rapid spreading at the air-liquid interface and produced a surface tension of <1 mN/m at minimum bubble size (gammamin) and 42 mN/m at maximum bubble size (gammamax) in the pulsating bubble surfactometer. The addition of 2% (w/w) SP-B to the preparation reduced the maximum surface tension to 33-35 mN/m, i.e. both gammamin and gammamax values were similar to those of natural surfactant preparations. Optimal in vitro characteristics were also obtained from a preparation containing SP-C(LKS), SP-B, DPPC and phosphatidylglycerol, i.e. when palmitic acid was omitted from the lipid mixture. SP-B containing surfactant preparations made up in Hepes buffer at pH 6.9, instead of in 150 mM NaCl, had similar biophysical activity provided that palmitic acid was omitted, but decreased activity in the presence of palmitic acid.

Radioisotope evaluation of the esophageal remnant and the gastric conduit after gastric pull-up esophagectomy

BACKGROUND

The act of swallowing after gastric pull-up esophagectomy has not been thoroughly investigated. The aim of this study was to evaluate deglutition in the esophageal remnant and in the gastric conduit in patients who have undergone this operation.

METHODS

The residual radionuclide activity was measured 15 seconds after a swallow in the esophageal remnant and at intervals up to a maximum of 120 minutes after a swallow in the gastric conduit. The scintigraphic rate of transit of a bolus in both areas was compared in patients who had anastomosis in the neck (n = 15) versus patients who had anastomosis in the chest (n = 19). Comparisons were also made between patients with and without symptoms of dysphagia. The scintigraphic measurements were also correlated with anastomotic diameters, measured with use of a volumetric balloon insufflation method, at 3, 6, and 12 months after operation.

RESULTS

There were no significant differences in esophageal residual radionuclide activity at 15 seconds after a swallow in the groups with anastomosis in the neck versus anastomosis in the chest, with 30% residual activity up to 12 months after operation in both groups (P = .24). In the patients as a whole the 50% gastric conduit emptying time of 44 to 61 minutes did not change during the first postoperative year (P = .12). There was no association between anastomotic diameter and residual activity in the remaining esophagus (P < .126). Moderate and severe dysphagia was reported in only a few patients, and there was no correlation between dysphagic symptoms and retention in the residual esophagus or slower emptying in the gastric conduit.

CONCLUSIONS

The amount of peristaltic activity in the remaining esophagus after esophagectomy with gastric replacement is unaffected by the level of the anastomosis. The gastric conduit empties slowly in all patients, and there is no correlation between the rate of emptying and either anastomotic diameter or symptoms of dysphagia.

[Growing genes cause neurological diseases]

A growing number of hereditary neurodegenerative disorders have been found to be caused by expansion of trinucleotide repeats. A smaller number of diseases such as fragile X syndrome, myotonic dystrophy, and Friedreich's ataxia, have been found to be due to expansions in non-coding DNA. In a large group of diseases, the expansion consists of CAG repeats in the coding region of the gene, producing an expanded polyglutamine sequence in the protein. Nine diseases have so far been identified as belonging to this group: Huntington's disease, spinobulbar muscular atrophy (SBMA), dentatorubral pallidoluysian atrophy (DRPLA), autosomal dominant "pure" spastic paraplegia (ADPSP), and five forms of spinocerebellar ataxia (SCA 1,2,3,6 and 7). Except for SBMA, all of the CAG repeat disorders are characterised by autosomal dominant heredity and anticipation (i.e., earlier onset age and increasing severity in successive generations). The mutated protein causes disease via an as yet unidentified gain-of-function mechanism in specific subsets of neurones. Today, DNA analysis permits the diagnosis of a trinucleotide disease in individual cases.

Antiplasmin correlates to arterial reactivity in a healthy population of 35-year-old men and women

OBJECTIVE

To study whether haemostasis function variables correlate with endothelial function and other vasomotion characteristics of the brachial artery in a randomly selected healthy population of 35-year-old men and women.

DESIGN

Endothelial function was measured as flow mediated dilatation (FMD) of the brachial artery during reactive hyperaemia and the nonendothelial dependent dilatation after sublingual nitroglycerin (NTG) was administered. Haemostasis and fibrinolysis function were estimated by analysis of von Willebrand factor, plasminogen activator inhibitor-1, antiplasmin and fibrinogen.

SETTING

A general medicine research centre and a university hospital.

SUBJECTS

Randomly chosen men (n = 53) and women (n = 56).

RESULTS

Univariate correlation analysis showed significant correlations between haemostasis factors, conventional risk factors for cardiovascular disease and indices of vasomotion of the brachial artery. In multivariate analysis, with haemostasis variables and conventional risk factors included, antiplasmin was the strongest explanatory variable for FMD. When antiplasmin was removed from the analysis, the r-value dropped from 0.46 to 0.35. Antiplasmin also correlated with NTG-induced dilatation (positively) and brachial diameter at rest (negatively), albeit less consistently.

CONCLUSIONS

Antiplasmin correlates significantly and independently to FMD, reflecting endothelial function, and also to brachial artery diameter at rest and nitroglycerin-induced dilatation. In multivariate analysis these correlations of antiplasmin to arterial characteristics were stronger than for 'conventional' risk factors, such as smoking, blood pressure and serum cholesterol.

Apolipoprotein A-I binds and inhibits the human antibacterial/cytotoxic peptide LL-37

The antibacterial and cytotoxic activity of the human cathelicidin peptide LL-37 is inhibited by plasma. Because LL-37 does not undergo rapid degradation in human plasma, we postulated that this inhibition results from binding of LL-37 to unidentified proteins. An LL-37 binding plasma protein has now been isolated by affinity chromatography. SDS-polyacrylamide gel electrophoresis of proteins that bound to an LL-37 column revealed one band with a molecular mass of about 26 kDa, and amino acid sequence analysis identified the protein as apolipoprotein A-I (apoA-I). Biomolecular interaction analysis using surface plasmon resonance showed that LL-37 and isolated apoA-I bind with an apparent Kd in the low micromolar range. 50 microM of apoA-I inhibits the antibacterial activity of 50 microM LL-37 by about 50% of the inhibition exhibited by plasma. In addition, anti-apoA-I IgG completely blocks the plasma inhibition of LL-37 antibacterial activity up to a peptide concentration of 25 microM and blocks most of the plasma inhibition at higher LL-37 concentrations. These results indicate that apoA-I is the main LL-37 binding protein in human plasma and may work as a scavenger of LL-37, thus suggesting a novel mechanism involved in the regulation of a cathelicidin peptide.

Determination of proteins, phosphatidylethanolamine, and phosphatidylserine in organic solvent extracts of tissue material by analysis of phenylthiocarbamyl derivatives

Amino acid analysis of organic solvent extracts of tissue material has been evaluated for determination of protein content. Conventional ninhydrin-based analysis does not allow determination of a large number of lipid-rich samples. Therefore, the hydrolyzed samples were treated with phenylisothiocyanate and the phenylthiocarbamyl (PTC) derivatives obtained were separated by reverse-phase HPLC. With this method, analysis of many lipid-rich samples is feasible. In addition, phosphatidylethanolamine and phosphatidylserine can then be determined together with the amino acid constituents. The PTC/reverse-phase HPLC method was used for analysis of chloroform/methanol extracts of spinal cord, lung, and bile after chromatography on Lipidex 5000 in methanol/ethylene chloride, 4:1 (v/v). The chromatography profiles show that in all tissue samples the proteins elute before the phospholipids. Consequently, a single step of Lipidex 5000 chromatography can be used to purify polypeptides present in organic solvent extracts. Using pulmonary surfactant extracts (with about 98% phospholipids and 1-2% proteins), we find that individual contents of surfactant proteins B and C can be determined by amino acid analysis.

Explosive rise of serum CA 125 following the rupture of ovarian endometrioma

Serum CA 125 concentration is seldom >100 IU/ml in endometriosis. We report a patient with ruptured endometrioma presenting with a very high CA 125 concentration, 9300 IU/ml. Elimination of endometriosis was followed by a sharp decrease in serum CA 125. We conclude that some of the CA 125 molecules from the ruptured endometriotic cyst may be transferred through the peritoneum, thereby increasing serum CA 125 concentration. The associated inflammatory reaction of the mesothelial cells of the peritoneum was probably the most important contributor to this phenomenon, as mesothelial cells are an important source of CA 125.

H-NS and StpA proteins stimulate expression of the maltose regulon in Escherichia coli

The nucleoid-associated protein H-NS is a major component of the chromosome-protein complex, and it is known to influence the regulation of many genes in Escherichia coli. Its role in gene regulation is manifested by the increased expression of several gene products in hns mutant strains. Here we report findings showing that H-NS and the largely homologous protein StpA play a positive role in the expression of genes in the maltose regulon. In studies with hns mutant strains and derivatives also deficient in the stpA gene, we found that expression of the LamB porin was decreased. Our results showed that the amounts of both LamB protein and lamB mRNA were greatly reduced in hns and hns-stpA mutant strains. The same results were obtained when we monitored the amount of transcription from the malEFG operon. The lamB gene is situated in the malKlamBmalM operon, which forms a divergent operon complex together with the malEFG operon. The activation of these genes depends on the action of the maltose regulon activator MalT and the global activator cyclic AMP receptor protein. Using a malT-lacZ translational fusion and antiserum raised against MalT to measure the expression of MalT, we detected reduced MalT expression in hns and hns-stpA mutant strains in comparison with the wild-type strain. Our results suggest that the H-NS and StpA proteins stimulate MalT translation and hence play a positive role in the control of the maltose regulon.

Pulmonary surfactant-associated polypeptide C in a mixed organic solvent transforms from a monomeric alpha-helical state into insoluble beta-sheet aggregates

In the 35-residue pulmonary surfactant-associated lipopolypeptide C (SP-C), the stability of the valyl-rich alpha-helix comprising residues 9-34 has been monitored by circular dichroism, nuclear magnetic resonance, and Fourier transform infrared spectroscopy in both a mixed organic solvent and in phospholipid micelles. The alpha-helical form of SP-C observed in freshly prepared solutions in a mixed solvent of CHCl3/CH3OH/0.1 M HCl 32:64:5 (v/v/v) at 10 degrees C undergoes within a few days an irreversible transformation to an insoluble aggregate that contains beta-sheet secondary structure. Hydrogen exchange experiments revealed that this conformational transition proceeds through a transition state with an Eyring free activation enthalpy of about 100 kJ mol(-1), in which the polypeptide segment 9-27 largely retains a helical conformation. In dodecylphosphocholine micelles, the helical form of SP-C was maintained after seven weeks at 50 degrees C. The alpha-helical form of SP-C thus seems to be the thermodynamically most stable state in this micellar environment, whereas its presence in freshly prepared samples in the aforementioned mixed solvent is due to a high kinetic barrier for unfolding. These observations support a previously proposed pathway for in vivo synthesis of SP-C through proteolytic processing from a 21-kDa precursor protein.

Structure and properties of surfactant protein C

Pulmonary surfactant contains less than 1 wt% of the very non-polar surfactant protein C (SP-C). In most animal species the major form of SP-C is a 35-residue peptide chain which contains two thioester-linked palmitoyl groups, giving a total molecular mass of 4.2 kDa. Several minor variants of SP-C exist, formed from N-terminal truncation, lysine palmitoylation, methionine oxidation and C-terminal esterification. The primary structure is evolutionarily conserved and SP-C appears to be the only constituent which is unique to pulmonary surfactant, indicating important and specific functions. The three-dimensional structure in an aqueous mixed organic solvent determined by NMR spectroscopy revealed one continuous 37 A long alpha-helix encompassing residues 9-34 as the only regular structural element. The central 23 A of the helix contains exclusively aliphatic residues with branched side-chains, mainly valines, and exposes an all-hydrophobic regular surface. The size of the entire helix perfectly matches the thickness of a fluid dipalmitoylphosphatidylcholine membrane, and the all-hydrophobic part of the helix matches the acyl-chain part of such a bilayer. This supports a transmembrane orientation of SP-C in pulmonary surfactant bilayers. In a phospholipid monolayer, the SP-C helix is tilted, thereby maximizing the interactions with the lipid acyl-chains also in this environment. The palmitoylcysteines of SP-C, which are located in the flexibly disordered N-terminal octapeptide segment, appear to be important both for integrity of the alpha-helical structure and for functional properties. Since the conformation of the N-terminal part in a phospholipid environment is not known, the mechanisms whereby the SP-C thioester-linked palmitoyl chains affect structure and function remain to be determined.