Functional annotation of conserved hypothetical proteins from Haemophilus influenzae Rd KW20

Haemophilus influenzae is a Gram negative bacterium that belongs to the family Pasteurellaceae, causes bacteremia, pneumonia and acute bacterial meningitis in infants. The emergence of multi-drug resistance H. influenzae strain in clinical isolates demands the development of better/new drugs against this pathogen. Our study combines a number of bioinformatics tools for function predictions of previously not assigned proteins in the genome of H. influenzae. This genome was extensively analyzed and found 1,657 functional proteins in which function of 429 proteins are unknown, termed as hypothetical proteins (HPs). Amino acid sequences of all 429 HPs were extensively annotated and we successfully assigned the function to 296 HPs with high confidence. We also characterized the function of 124 HPs precisely, but with less confidence. We believed that sequence of a protein can be used as a framework to explain known functional properties. Here we have combined the latest versions of protein family databases, protein motifs, intrinsic features from the amino acid sequence, pathway and genome context methods to assign a precise function to hypothetical proteins for which no experimental information is available. We found these HPs belong to various classes of proteins such as enzymes, transporters, carriers, receptors, signal transducers, binding proteins, virulence and other proteins. The outcome of this work will be helpful for a better understanding of the mechanism of pathogenesis and in finding novel therapeutic targets for H. influenzae.

Role of N-terminal residues on folding and stability of C-phycoerythrin: simulation and urea-induced denaturation studies

The conformational state of biliproteins can be determined by optical properties of the covalently linked chromophores. Recently determined crystal structure of truncated form of α-subunit of cyanobacterial phycoerythrin (αC-PE) from Phormidium tenue provides a new insight into the structure-function relationship of αC-PE. To compare their stabilities, we have measured urea-induced denaturation transitions of the full length αC-PE (FL-αC-PE) and truncated αC-PE (Tr-αC-PE) followed by observing changes in absorbance at 565 nm, fluorescence at 350 and 573 nm, and circular dichroism at 222 nm as a function of [urea], the molar concentration of urea. The transition curve of each protein was analyzed for ΔG(D)(0), the value of Gibbs free energy change on denaturation (ΔG(D)) in the absence of urea; m, the slope (=∂∆G(D)/∂[urea]), and C(m), the midpoint of the denaturation curve, i.e. [urea] at which ΔG(D) = 0. A difference of about 10% in ΔG(D)(0) observed between FL-αC-PE and Tr-αC-PE, suggests that the two proteins are almost equally stable, and the natural deletion of 31 residues from the N-terminal side of the full length protein does not alter its stability. Furthermore, normalization of probes shows that the urea-induced denaturation of both the proteins is a two-state process. Folding of both structural variants (Tr-αC-PE and FL-αC-PE) of P. tenue were also studied using molecular dynamics simulations at 300 K. The results show clearly that the stability of the proteins is evenly distributed over the whole structure indicating no significant role of N-terminal residues in the stability of both proteins.

High resolution crystal structure of human β-glucuronidase reveals structural basis of lysosome targeting

Human β-glucuronidase (GUS) cleaves β-D-glucuronic acid residues from the non-reducing termini of glycosaminoglycan and its deficiency leads to mucopolysaccharidosis type VII (MPSVII). Here we report a high resolution crystal structure of human GUS at 1.7 Å resolution and present an extensive analysis of the structural features, unifying recent findings in the field of lysosome targeting and glycosyl hydrolases. The structure revealed several new details including a new glycan chain at Asn272, in addition to that previously observed at Asn173, and coordination of the glycan chain at Asn173 with Lys197 of the lysosomal targeting motif which is essential for phosphotransferase recognition. Analysis of the high resolution structure not only provided new insights into the structural basis for lysosomal targeting but showed significant differences between human GUS, which is medically important in its own right, and E. coli GUS, which can be selectively inhibited in the human gut to prevent prodrug activation and is also widely used as a reporter gene by plant biologists. Despite these differences, both human and E. coli GUS share a high structure homology in all three domains with most of the glycosyl hydrolases, suggesting that they all evolved from a common ancestral gene.

Testing the ability of non-methylamine osmolytes present in kidney cells to counteract the deleterious effects of urea on structure, stability and function of proteins

Human kidney cells are under constant urea stress due to its urine concentrating mechanism. It is believed that the deleterious effect of urea is counteracted by methylamine osmolytes (glycine betaine and glycerophosphocholine) present in kidney cells. A question arises: Do the stabilizing osmolytes, non-methylamines (myo-inositol, sorbitol and taurine) present in the kidney cells also counteract the deleterious effects of urea? To answer this question, we have measured structure, thermodynamic stability (ΔG D (o)) and functional activity parameters (K m and k cat) of different model proteins in the presence of various concentrations of urea and each non-methylamine osmolyte alone and in combination. We observed that (i) for each protein myo-inositol provides perfect counteraction at 1∶2 ([myo-inositol]:[urea]) ratio, (ii) any concentration of sorbitol fails to refold urea denatured proteins if it is six times less than that of urea, and (iii) taurine regulates perfect counteraction in a protein specific manner; 1.5∶2.0, 1.2∶2.0 and 1.0∶2.0 ([taurine]:[urea]) ratios for RNase-A, lysozyme and α-lactalbumin, respectively.

Search of potential inhibitor against New Delhi metallo-beta-lactamase 1 from a series of antibacterial natural compounds

Background:

New Delhi metallo-β-lactamase-1 (NDM-1)-producing Gram-negative bacteria are today's major worldwide health concern. The enzyme NDM-1 provides bacterial resistance by its hydrolytic activity against the β-lactam ring of antibiotics. Inhibition of NDM-1 may prevent the hydrolysis of β-lactam ring of the antibiotics, and therefore, plays an important role against antibacterial resistance.

Materials and Methods:

Here we made an attempt to design suitable inhibitors against NDM-1 from different natural antibacterial compounds using molecular docking approach.

Results:

We observed that natural compounds such as Nimbolide and Isomargololone are showing an appreciable IC50 value as well as significant binding energy value for NDM-1. We further observed these compounds showing better affinity to NDM-1 on comparison with 14 β-lactam antibiotics.

Conclusion:

Finally, our study provides a platform for the development of a potent inhibitor of NDM-1, which may be considered as a potential drug candidate against bacterial resistance.

Fluorescent dye conjugates of rabbit arylsulfatase A as a biological tracer for protein endocytosis

Fluorescent dye conjugates of arylsulfatase A (ASA) from rabbit liver were prepared at pH 9.0 in 0.1 M sodium bicarbonate buffer. The modification of amino or sulphadryl groups by dichlorotriazinylamino-fluorescein or Lucifer yellow fluorescent dyes did not alter the characteristic features of the enzyme molecule such as enzyme activity, dimerization of the protein molecule at pH 4.5 and anomalous kinetics of the native enzyme. The fluorescence intensity of the Lucifer yellow enzyme conjugates were quenched when the pH of the protein solution was changed from pH 7.5 to 4.5. Therefore, the Lucifer yellow enzyme conjugate can be used to study the kinetics of pH-dependent association and dissociation of the ASA. Availability of such fluorescent dyes conjugates of ASA or other lysosomal enzyme may be used as a biological tracer to study the receptor dependent endocytosis of enzyme molecules.

The role of key residues in structure, function, and stability of cytochrome-c

Cytochrome-c (cyt-c), a multi-functional protein, plays a significant role in the electron transport chain, and thus is indispensable in the energy-production process. Besides being an important component in apoptosis, it detoxifies reactive oxygen species. Two hundred and eighty-five complete amino acid sequences of cyt-c from different species are known. Sequence analysis suggests that the number of amino acid residues in most mitochondrial cyts-c is in the range 104 ± 10, and amino acid residues at only few positions are highly conserved throughout evolution. These highly conserved residues are Cys14, Cys17, His18, Gly29, Pro30, Gly41, Asn52, Trp59, Tyr67, Leu68, Pro71, Pro76, Thr78, Met80, and Phe82. These are also known as "key residues", which contribute significantly to the structure, function, folding, and stability of cyt-c. The three-dimensional structure of cyt-c from ten eukaryotic species have been determined using X-ray diffraction studies. Structure analysis suggests that the tertiary structure of cyt-c is almost preserved along the evolutionary scale. Furthermore, residues of N/C-terminal helices Gly6, Phe10, Leu94, and Tyr97 interact with each other in a specific manner, forming an evolutionary conserved interface. To understand the role of evolutionary conserved residues on structure, stability, and function, numerous studies have been performed in which these residues were substituted with different amino acids. In these studies, structure deals with the effect of mutation on secondary and tertiary structure measured by spectroscopic techniques; stability deals with the effect of mutation on T m (midpoint of heat denaturation), ∆G D (Gibbs free energy change on denaturation) and folding; and function deals with the effect of mutation on electron transport, apoptosis, cell growth, and protein expression. In this review, we have compiled all these studies at one place. This compilation will be useful to biochemists and biophysicists interested in understanding the importance of conservation of certain residues throughout the evolution in preserving the structure, function, and stability in proteins.

Why is glycine not a part of the osmoticum in the urea-rich cells?

Kidney cells of animals including human and marine invertebrates contain high amount of the protein denaturant, urea. Methylamine osmolytes are generally believed to offset the harmful effects of urea on proteins in vitro and in vivo. In this study we have investigated the possibility of glycine to counteract the effects of urea on three proteins by measuring thermodynamic stability, ΔGD° and functional activity parameters (K(m) and k(cat)). We discovered that glycine does not counteract the effects of urea in terms of both protein stability and functional activity. We also observed that the glycine alone is compatible with enzymes function and increases protein stability in terms of T(m) (midpoint of thermal denaturation) to a great extent. Our study indicates that a most probable reason for the absence of a stabilizing osmolyte, glycine in the urea-rich cells is due to the fact that this osmolyte is non-protective to macromolecules against the hostile effects of urea, and hence is not chosen by evolutionary selection pressure.

Characterisation of mutations and molecular studies of type 2 von Willebrand disease

Type 2 von Willebrand disease (VWD) is characterised by qualitative defects in von Willebrand factor (VWF). Exon 28 of the VWF gene is known to be a hot spot for type 2 VWD mutations. The goal of this study was to characterise the mutations in VWF exon 28 and understand the molecular basis of phenotypes through in vitro and in silico studies. Mutation screening was performed in 56 type 2 VWD patients through direct sequencing. Expression vectors for five mutations were transiently expressed in 293-EBNA cells to understand the mutations pathology. Furthermore, in silico structure analysis was performed for 13 missense mutations. A total of 16 including eight novel mutations were detected in 23 (41%) patients. Of these, 15 were missense (including seven V1439M, A1464P, M1495L, I1509V, R1527Q, N1635I and A1647D novel ones) and one was a novel gene conversion. Expression studies and characterisation of recombinant VWF suggested the loss of VWF function for mutants P1266Q, V1439M and N1635I and gain of function for mutant R1308C. No apparent defect was seen in mutant N1231S. In silico structure analysis suggested the probable gain or loss of hydrogen/van der Waals interactions in 10 mutant proteins. In conclusion, type 2A mutations and gene conversion were found to be a common cause of type 2 VWD. Expression studies suggest the mutations N1635I for type 2A(II), P1266Q and V1439M for type 2M, R1308C for type 2B VWD and N1231S as a non-causative variant. Moreover, in silico studies of the mutants show the probable cause of respective phenotypes.

Kinetic and structural studies on the interactions of heparin and proteins of human seminal plasma using surface plasmon resonance

Heparin is naturally occurring polysaccharides which interacts with seminal plasma proteins and regulate multiple steps in fertilization process. Qualitative and quantitative information regarding the affinity for heparin-seminal plasma proteins interactions is not generally well documented and there are no reports of a comprehensive analysis of these interactions in human seminal plasma. Such information should improve our understanding of how GAGs especially heparin present in the reproductive tract regulate fertilization. In this study, we use SPR to study interactions of heparin with various seminal plasma heparin-binding proteins (HBPs). HBPs like lactoferrin (LF), fibronectin fragment (FNIII), semenogelinI (SGI) and prostate specific antigen (PSA) all bind heparin with different binding kinetics and affinities. Kinetic data suggests that FNIII binds heparin with a high affinity (KD=3.2 nM), while PSA binds heparin with a micromolar affinity (KD=11.1 μM). Preincubation of SGI with heparin inhibits the binding of SGI to immobilized PSA in a dose-dependent manner, while FNIII incubated with heparin binds with an increased affinity to PSA. Solution-competition studies show that the minimum size of a heparin oligosaccharide capable of binding with PSA is greater than a tetrasaccharide, with LF and SGI is larger than a hexasaccharide and for FNIII is larger than an octasaccharide.

Structure, function and applications of carbonic anhydrase isozymes

The carbonic anhydrases enzymes (CAs, EC 4.2.1.1) are zinc containing metalloproteins, which efficiently catalyse the reversible conversion of carbon dioxide to bicarbonate and release proton. These enzymes are essentially important for biological system and play several important physiological and patho-physiological functions. There are 16 different alpha-carbonic anhydrase isoforms studied, differing widely in their cellular localization and biophysical properties. The catalytic domains of all CAs possess a conserved tertiary structure fold, with predominately β-strands. We performed an extensive analysis of all 16 mammalian CAs for its structure and function in order to establish a structure-function relationship. CAs have been a potential therapeutic target for many diseases. Sulfonamides are considered as a strong and specific inhibitor of CA, and are being used as diuretics, anti-glaucoma, anti-epileptic, anti-ulcer agents. Currently CA inhibitors are widely used as a drug for the treatment of neurological disorders, anti-glaucoma drugs, anti-cancer, or anti-obesity agents. Here we tried to emphasize how CAs can be used for drug discovery, design and screening. Furthermore, we discussed the role of CA in carbon capture, carbon sensor and metabolon. We hope this review provide many useful information on structure, function, mechanism, and applications of CAs in various discipline.

Functional role of glutamine 28 and arginine 39 in double stranded RNA cleavage by human pancreatic ribonuclease

Human pancreatic ribonuclease (HPR), a member of RNase A superfamily, has a high activity on double stranded (ds) RNA. By virtue of this activity HPR appears to be involved in the host-defense against pathogenic viruses. To delineate the mechanism of dsRNA cleavage by HPR, we have investigated the role of glutamine 28 and arginine 39 of HPR in its activity on dsRNA. A non-basic residue glycine 38, earlier shown to be important for dsRNA cleavage by HPR was also included in the study in the context of glutamine 28 and arginine 39. Nine variants of HPR respectively containing Q28A, Q28L, R39A, G38D, Q28A/R39A, Q28L/R39A, Q28A/G38D, R39A/G38D and Q28A/G38D/R39A mutations were generated and functionally characterized. The far-UV CD-spectral analysis revealed all variants, except R39A, to have structures similar to that of HPR. The catalytic activity of all HPR variants on single stranded RNA substrate was similar to that of HPR, whereas on dsRNA, the catalytic efficiency of all single residue variants, except for the Q28L, was significantly reduced. The dsRNA cleavage activity of R39A/G38D and Q28A/G38D/R39A variants was most drastically reduced to 4% of that of HPR. The variants having reduced dsRNA cleavage activity also had reduction in their dsDNA melting activity and thermal stability. Our results indicate that in HPR both glutamine 28 and arginine 39 are important for the cleavage of dsRNA. Although these residues are not directly involved in catalysis, both arginine 39 and glutamine 28 appear to be facilitating a productive substrate-enzyme interaction during the dsRNA cleavage by HPR.

Structural and functional analysis of human prostatic acid phosphatase

Prostatic acid phosphatase (PAP) is the most abundant phosphatase in human prostate tissue/secretions. It is a clinically important protein for its relevance as a biomarker of prostate carcinoma. Furthermore, it has a potential role in fertilization. We describe here most of the features of PAP including gene regulation, gene/protein structure, functions, its role in tumor progression and evolutionary features. PAP has phosphatase activity and is an extensively studied biomarker of prostate cancer. The major action of PAP is to dephosphorylate macromolecules with the help of catalytic residues (His(12) and Asp(258)) that are located in the cleft between two domains. This article will be of great interest to all those scientists who are working in the area of prostate pathophysiology.

Progastriscin: structure, function, and its role in tumor progression

Progastricsin (PGC) is a major seminal plasma protein having aspartyl proteinases-like activity and showing close sequence similarity to pepsins. PGC is also present as zymogen in gastric mucosa. In this article, we have reviewed all important features of PGC. Furthermore, we have compared all features of PGC with those of different aspartyl proteinases. The complete amino acid sequence of PGC reveals that it is composed of 374 residues (gastricsin moiety of 331 residues and the activation segment of 43 residues). The gene of human PGC is located at single locus on chromosome 6, whereas the human pepsinogen genetic locus is polymorphic and codes for at least three distinct polypeptide sequences on chromosome 11. The major useful function of PGC includes production of pro-antimicrobial substance in seminal plasma. The crystal structure of human PGC is known, which shows that it is quite similar to that of porcine pepsinogen. The tertiary structure of PGC is comprised of commonly bilobal structure with a large active-site cleft between the lobes. Two aspartate residues in the center of the cleft, namely Asp32 and Asp215, function as catalytic residues. The sequence and structural features of PGC indicate that it is diverged from its pepsinogen ancestor in the early phase of the evolution of gastric aspartyl proteinases. Our detailed review of PGC structure, function and activation mechanism will also be of interest to cancer biologists as well as gastroenterologists.

Fragile histidine triad protein: structure, function, and its association with tumorogenesis

BACKGROUND

The human fragile histidine triad (FHIT) gene is a putative tumor suppressor gene, which is located at chromosome region 3p14.2. It was suggested that the loss of heterozygosity (LOH), homozygous deletions, and abnormal expression of the FHIT gene were involved in several types of human malignancies.

MATERIALS AND METHODS

To determine the role of FHIT in various cancers, we have performed structural and functional analysis of FHIT in detail.

RESULTS AND DISCUSSION

The protein FHIT catalyzes the Mg(2+) dependent hydrolysis of P1-5 cent-O-adenosine-P3-5 cent-O-adenosine triphosphate, Ap3A, to AMP, and ADP. The reaction is thought to follow a two-step mechanism. Histidine triad proteins, named for a motif related to the sequence H-cent-H-cent-H-cent-cent- (cent, a hydrophobic amino acid), belong to superfamily of nucleotide hydrolases and transferases. This enzyme acts on the R-phosphate of ribonucleotides, and contain a approximately 30-kDa domain that is typically a homodimer of approximately 15 kDa polypeptides with catalytic site.

CONCLUSION

Here we have gathered information is known about biological activities of FHIT, the structural and biochemical bases for their functions. Our approach may provide a comparative framework for further investigation of FHIT.

Proteomic analysis of heparin-binding proteins from human seminal plasma: a step towards identification of molecular markers of male fertility

Glycosaminoglycans, especially heparin, are involved in various cell processes such as apoptosis, cell cycle control, platelet activation, capacitation, acrosome reaction and sperm decondensation. Heparin-binding proteins (HBPs) are essential constituents of human seminal fluid, which bind to sperm lipids containing the phosphorylcholine group and mediate the fertilization process. We utilized a proteomic set-up consisting of affinity chromatography, isoelectric focusing (IEF) coupled with matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI TOF/MS) for protein analysis of human HBPs. We resolved 70 different spots on two-dimensional (2-D) gel and subsequently identifi ed these proteins. Forty different types of proteins were identified. Functional analysis revealed that 38% of the proteins belonged to the enzyme category, 20% were involved in RNA processing and transcription, 18% in structure and transport function, and 16% in cell recognition and signal transduction. We also identified 8% of proteins with unknown functions, although their expression in seminal fluid has been documented. Proteins of seminal fluid that bind heparin may be directly involved in sperm capacitation and acrosome reaction (AR), which are the two critical steps for fertilization. This information on HBPs would be useful for identifying potential biomarkers of fertility in the near future.

Evaluation of serum squamous cell carcinoma antigen as a novel biomarker for diagnosis of hepatocellular carcinoma in Egyptian patients

BACKGROUND

Hepatocellular carcinoma (HCC) is the fifth most common malignancy in the world. In Egypt, HCC was reported to account for about 4.7% of chronic liver disease (CLD) patients. Squamous cell carcinoma antigen (SCCA) has been reported to be strongly expressed in HCC tissue hampering its extensive use in clinical practice.

AIM

To evaluate the clinical usefulness of serum SCCA levels as a serological marker for early detection of HCC among high-risk patients compared to AFP.

MATERIALS AND METHODS

The study comprised of three groups. Group A included 30 patients with CLD diagnosed based on clinical, laboratory, and ultrasonographical investigations; group B included 49 patients with HCC diagnostically confirmed by spiral CT, elevated alfafetoprotein (AFP), and/or liver biopsy; and group C, the control group, included 15 healthy subjects matched for age and sex. All groups were subjected to thorough history taking, full clinical examination, and laboratory investigations including liver functions, viral markers, and AFP and SCCA estimation using ELISA technique.

RESULTS

This study revealed a highly significant difference between patients with HCC, CLD, and controls regarding serum SCCA levels (5.138 +/- 7.689, 1.133 +/- 0.516, and 0.787 +/- 0.432 ng/ml, respectively). SCCA level was persistently elevated in patients with HCC with normal AFP levels representing its useful role in early detection and follow-up of patients treated for HCC. The area under the curve (AUC) of SCCA was 0.869 (95% CI 0.783-0.929), the cut-off value was established at 1.5 ng/ml with sensitivity of 77.6% and specificity of 84.4%). The difference between AUC of SCCA and that of AFP was 0.09 which mounted statistical significance.

CONCLUSIONS

SCCA could represent a useful tool as a marker for detection of HCC.

Heparin-binding proteins of human seminal plasma: purification and characterization

Human seminal plasma (HuSP) contains several proteins that bind heparin and related glycosaminoglycans. Heparin binding proteins (HBPs) from seminal plasma have been shown to participate in modulation of capacitation or acrosome reaction and thus have been correlated with fertility in some species. However, these have not been studied in detail in human. The objective of this study was to purify major HBPs from HuSP in order to characterize these proteins. HBPs were isolated by affinity-chromatography on Heparin-Sepharose column, purified by reverse-phase high-performance liquid chromatography (RP-HPLC) and Size-exclusion chromatography and checked for purity on sodium-dodecyl PAGE (SDS-PAGE). Identification of HBPs was done by matrix-assisted laser desorption-ionization-time-of-flight-mass spectrometry (MALDI-TOF-MS). Here we report the purification and identification of seven HBPs in seminal fluid. The major HBPs are lactoferrin and its fragments, semenogelin I fragments, semenogelin II, prostate specific antigen, homolog of bovine seminal plasma-proteins (BSP), zinc finger protein (Znf 169) and fibronectin fragments. In this study we are reporting for the first time the purification and identification of BSP-homolog and Znf 169 from HuSP and classified them as HBPs. Here we report the purification of seven clinically important proteins from human seminal fluid through heparin affinity chromatography and RP-HPLC, in limited steps with higher yield.

Crystal structure of the novel complex formed between zinc alpha2-glycoprotein (ZAG) and prolactin-inducible protein (PIP) from human seminal plasma

This is the first report on the formation of a complex between zinc alpha2-glycoprotein (ZAG) and prolactin-inducible protein (PIP). The complex was purified from human seminal plasma and crystallized using 20% polyethylene glycol 9000 and 5% hexaethylene glycol. The structure of the complex has been determined using X-ray crystallographic method and refined to an R(cryst) of 0.199 (R(free)=0.239). The structure of ZAG is broadly similar to the structure of serum ZAG. The scaffolding of PIP consists of seven beta-strands that are organized in the form of two antiparallel beta-pleated sheets, resulting in the formation of a sandwiched beta-sheet. The amino acid sequence of PIP contains one potential N-glycosylation site at Asn77, and the same is found glycosylated with four sugar residues. The structure of the complex shows that the beta-structure of PIP is ideally aligned with the beta-structure of domain alpha3 of ZAG to form a long interface between two proteins. The proximal beta-strands at the long interface are arranged in an antiparallel manner. There are 12 hydrogen bonds and three salt bridges between ZAG and PIP. At the two ends of vertical interface, two salt bridges are formed between pairs of Lys41-Asp233 and Lys68-Glu229. On the perpendicular interface involving alpha1-alpha2 domains of ZAG and a loop of PIP, another salt bridge is formed. The internal space at the corner of the L-shaped structure is filled with solvent molecules including a carbonate ion. The overall buried area in the complex is approximately 914 A(2), which is considerably higher than the 660 A(2) reported for the class I major histocompatibility complex structures.

Zinc alpha 2-glycoprotein: a multidisciplinary protein

Zinc alpha 2-glycoprotein (ZAG) is a protein of interest because of its ability to play many important functions in the human body, including fertilization and lipid mobilization. After the discovery of this molecule, during the last 5 decades, various studies have been documented on its structure and functions, but still, it is considered as a protein with an unknown function. Its expression is regulated by glucocorticoids. Due to its high sequence homology with lipid-mobilizing factor and high expression in cancer cachexia, it is considered as a novel adipokine. On the other hand, structural organization and fold is similar to MHC class I antigen-presenting molecule; hence, ZAG may have a role in the expression of the immune response. The function of ZAG under physiologic and cancerous conditions remains mysterious but is considered as a tumor biomarker for various carcinomas. There are several unrelated functions that are attributed to ZAG, such as RNase activity, regulation of melanin production, hindering tumor proliferation, and transport of nephritic by-products. This article deals with the discussion of the major aspects of ZAG from its gene structure to function and metabolism.

Structural model of human PSA: a target for prostate cancer therapy

Based on unique biology of prostate cancer, prostate-specific antigen could be a useful target for prostate cancer therapies. Such targeting requires the identification of highly selective inhibitor-binding sites. Three-dimensional structure was calculated by homology modeling. The overall structure of human prostate-specific antigen is composed of two beta-barrel domain, kallikrein loop and active-site triad His57, Asp102, and Ser195. Structure of human prostate-specific antigen is quite similar to hK-1 and HPK-3. The major differences were observed at kallikrein loop and position of active site. The substrate-binding pocket is predominated by hydrophobic residues and the bottom of the specificity pocket contains Ser189 as in chymotrypsin, which provides substrate specificity. The hydrophobic, and preferentially aromatic (Trp215), amino acid residues are determinant of substrate binding due to the presence of hydrophobic crevice between Tyr99 and Trp215. Crystal structure of human prostate-specific antigen is not determined till now and hence the report on an accurate and comparative model of human prostate-specific antigen is probably to help in understanding their functional network and finally could be helpful in structure-based rational drug designing.

Proteomic approach for purification of seminal plasma proteins involved in tumor proliferation

Human seminal plasma contains a large array of proteins required for the normal physiology and metabolism of spermatozoa. These are mainly secreted from prostate epithelium, testes, and seminal vesicles. Fortunately, many of these are found to be present at elevated concentration in seminal plasma and act as a biomarker of different carcinomas as their levels are also enhanced in serum and are found to be involved in tumor progression and metastasis apart from fertility. The proteins which were overexpressed in the seminal plasma of prostate carcinoma patients were identified by 2-DE and MALDI-TOF/MS. We have designed a strategy to purify these four proteins prostate specific antigen (PSA), prostatic acid phosphatase (PAP), Zinc alpha2-glycoprotein (ZAG), and progastricsin (PG), together in homogeneity by using simple chromatographic techniques. Acidic and basic fractions of human seminal plasma were separated by ion exchange chromatography and further purified by gel permeation chromatography. Our results form a new and valuable resource for those attempting structure-based drug designing for prostate and other cancers where the amount of proteins is required in plenty and in native form.

Structure-guided design of peptidic ligand for human prostate specific antigen

Prostate specific antigen (PSA) is a member of kallikrein family having serine protease-like activity and acts as a prognostic marker of prostate carcinoma. Various studies have been performed on inhibition of PSA and such targeting requires the identification of highly selective peptide inhibitors. PSA was purified from human seminal plasma by rapid and efficient methods, and binding studies for various peptides were carried out by fluorescence spectroscopy and SPR. The 'S' of PSA is predominated by hydrophobic residues, and hence many hydrophobic peptides were used to determine their binding affinity to PSA by fluorescence spectroscopy. We observed that LLFW, FFKW, and KFW binds strongly to PSA, among them LLFW showed strong binding. SPR also showed strong binding affinity of PSA toward peptides with hydrophobic and basic residues. Among the peptides used, FWYS showed dramatic increase in binding affinity (10(-10) M). The peptides analyzed for binding studies, suggests that peptide with Trp residue along with basic or hydrophobic amino acids may be useful for designing specific inhibitors for PSA. The strong affinities of designed peptides for PSA can be a valuable tool for designing therapeutic agents for prostate carcinomas.

Effect of midgut bacteria of Culex pipiens L. on digestion and reproduction

An investigation was carried out to evaluate the influence of symbiotic bacteria associated with Culex pipiens L. on pre-oviposition and blood meal digestion periods, and reproductive potential (fecundity and fertility). Aposymbiotic females were obtained by feeding the normal females on 10% sucrose solution mixed with antibiotic (Tarivid) for three days before feeding them on normal blood meals from a pigeon host. A total of 4 genera were previously isolated from the midgut of C. pipiens. These genera were: Bacillus, Streptococcus, Staphylococcus, and Salmonella and Shigella. It seems that the period of blood meal digestion preceded the pre-oviposition period of both bacterial free females and bacterial-free females treated with one of the aforementioned bacteria. In addition, it is obviously clear that, the presence of the two bacterial genera: Bacillus and Staphylococcus in the midgut of C. pipiens is essential for normal and high fecundity. Generally, it is evident that the symbionts (gut bacteria) are essential for the completion of embryonic development.

Ovarian cancer-induced immunosuppression: relationship to tumor necrosis factor-alpha (TNF-alpha) release from ovarian tissue

Cytokines have been reported to be potential biological markers of, disease status in cancer patients. Tumor necrosis factor-alpha (TNF-alpha) is a key cytokine released from monocytes and macrophages. TNF-alpha is involved in essential biological functions such as immunoregulation, modulation of cell growth and differentiation. In this work, the role of TNF-alpha release in ovarian cancer patients was investigated. Fifty-five patients with ovarian cancer and 20 controls of matched age and parity were included in this study. TNF-alpha concentrations were measured in sera and cytosolic fractions of both groups. The results demonstrated a significant increase in TNF-alpha concentrations among patients compared to the control subjects (P < 0.001). Furthermore, a non-significant increase (P = 0.05, was observed between the different types (serous, Mucinous, and endometrioid) of epithelial ovarian cancers. Also TNF-alpha concentrations did not correlate with the disease stage. Moreover, immunohistochemical analysis of tissue specimens stained for TNF-alpha was positive in malignant lesions and negative for the normal ovarian tissue. These findings confirmed the TNF-alpha kinetics obtained by ELISA assays. Interestingly, TNF-alpha levels were also elevated in culture supernatants of PBMC stimulated by cytosolic fractions from malignant ovarian tissues. Blastogenic assays using cytosolic fractions from malignant ovarian specimens to stimulate healthy donor peripheral blood mononuclear cells (PBMC) showed a marked decrease in 3H-thymidine uptake compared to the cells stimulated by normal cytosols. To establish a cause-effect relationship between TNF-alpha release and inhibition of cell proliferation, the experiments showed that 3H-thymidine uptake by PBMC was markedly inhibited by recombinant human TNF-alpha (rh TNF-alpha) and that inhibition was significantly reversed when TNF-alpha monoclonal antibody was added to the cells. The data presented in this work indicate that TNF-alpha may play an important role in the biology of ovarian cancer and hence, tumor pathogenesis.

Cis-platinum-induced immunosuppression: relationship to melatonin in human peripheral blood mononuclear cells

OBJECTIVES

The purpose of this study was to investigate the immunomodulatory effect of melatonin (MLT) on human peripheral blood mononuclear cells (PBMC) and to address its effects on Cis-platinum (CDDP)-induced cytotoxicity.

METHODS AND RESULTS

The obtained data from this study revealed that treatment of cells with MLT (100 microg/ml) for 24 h enhanced cell viability. When cells were exposed to CDDP (5 microg/ml), cell proliferation in response to phytohaemagglutinin (PHA) stimulation was reduced by 49.63% compared to control cells as detected by 3[H]-thymidine uptake. Furthermore, Cis-platinum significantly depleted intracellular glutathione (GSH) levels by approximately 47% below that of untreated cells and led to apoptotic changes in the target cells as evidenced by DNA fragmentation (45% compared to 5% in control cells as measured by diphenylamine assay). DNA fragmentation was also confirmed by agarose gel electrophoresis. However, MLT enhanced cell proliferation by approximately 8.63% above the control values, and counteracted the antiproliferative effect of CDDP. The GSH levels were significantly increased in response to MLT (71% above control values) and it protected the cells against GSH depletion induced by CDDP. Moreover, DNA fragmentation and laddering produced by CDDP were significantly reduced or even disappeared when the cells were pretreated with MLT or the latter was simultaneously added with CDDP.

CONCLUSIONS

The findings from this study indicated that melatonin is a potent immunomodulatory hormone that protects PBMC against cis-platinum-induced immunosuppressive effects. These effects might improve the patients' response to cis-platinum therapy and, therefore, their survival rates.

Epstein-Barr virus, human papillomavirus, and flow cytometric cell cycle kinetics in nasopharyngeal carcinoma and inverted papilloma among Egyptian patients

It is widely accepted that the Epstein-Barr virus is etiologically associated with the development of nasopharyngeal carcinoma. The human papillomavirus is also associated with inverted papilloma. We used the polymerase chain reaction technique to detect both viruses in both types of tumors. Flow cytometry was also used to study the DNA pattern and proliferative behavior of the tumors in relation to the viruses. EBV was detected in 13/20 (65%) of NPC specimens, and in none of IP (n = 10) or control specimens (n = 10). This indicates the contribution of EBV as an etiologic factor in NPC. Five cases of NPC (25%) were positive for HPV 16, two of them were EBV positive. Four HPV 16 positive cases were found among cases with inverted papilloma, but none among the control cases. Flow cytometry revealed that all NPC, IP, and control samples were diploid except one aneuploid NPC sample. Proliferative capacity (PC) of primary tumors was predictive of tumor recurrence in NPC. Using 13.6% as a cut-off point for PC, we were able to discriminate between high risk and low risk groups with 100% sensitivity and 86% specificity. PC can be used as a baseline prognostic parameter in NPC, making it possible to modify courses of treatment in an attempt to inhibit tumor recurrence.

Human cytomegalovirus-induced immunosuppression. Relationship to tumor necrosis factor-dependent release of arachidonic acid and prostaglandin E2 in human monocytes

Cytomegalovirus (CMV) has been associated with immunosuppression. Previously CMV was reported to interfere with signal transduction pathways in T cells. In this report the mechanisms underlying CMV-mediated immunosuppression were examined. Supernatants of CMV (Strains C-87, AD-169)-infected primary human monocyte (MO) cultures inhibited mitogenic T cell proliferative responses by > 95%. The inhibitory activity was observed 24 h through day 7 postinfection. The infection of MO was associated with a sustained elevation of intracellular levels of cAMP and the release of arachidonic acid (AA) and its metabolite PGE2 (activator of adenylate cyclase) in culture supernatants. The AA release was incidentally associated with TNF-alpha production. Monoclonal antibodies to TNF-alpha and pentoxyphylline (inhibitor of TNF synthesis) inhibited both AA and PGE2 release. The release of AA required protein synthesis and occurred under conditions consistent with the expression of CMV immediate early genes. Treatment of MO cultures at time of infection with 100 microM indomethacin or 1 microg of TNF-alpha mAb abolished the CMV-induced T cell inhibitory activity of the supernatants by 100%. These data suggest that TNF dependent release of AA and PGE2 contributes to CMV-induced immunosuppression.

HIV-induced TNF-alpha regulates arachidonic acid and PGE2 release from HIV-infected mononuclear phagocytes

Arachidonic acid (AA) has been shown to interact with transmembrane signaling pathways involved in T-cell activation. The latter have been shown to be impaired in lymphocytes obtained from HIV-infected patients. In the present study, AA and its metabolite, PGE2, released from differentiating human mononuclear phagocytes in response to HIV infection, and their relationship to HIV replication and TNF-alpha production were examined. The macrophage (M phi) cultures were more permissive for HIV replication than monocyte (MO) cultures. AA release in response to HIV infection was observed in both MO and M phi with a peak at 24 hr postinfection (p.i.). This AA release was 3.8- and 6-fold that of uninfected MO and M phi cultures, respectively. Supernatants from MO and M phi cultures at the peak of AA production inhibited [3H]thymidine uptake of peripheral blood mononuclear cells in response to PHA by 45 and 54%. At 24 hr p.i., PGE2 production was increased in both MO and M phi cultures. This increase was associated with a 1.2- and 20-fold inhibition of IL-1 production, respectively. TNF release, however, increased through day 14 p.i. Treating mock-infected MO with recombinant TNF-alpha induced AA release. Monoclonal antibodies to TNF inhibited this release by 80%. TNF (0.01-0.4 microgram/ml) added exogenously to MO produced a biphasic pattern of AA release; while low concentrations were stimulatory, higher concentrations were inhibitory. Treating monocyte and macrophage cultures with mAb to TNF-alpha inhibited the HIV-induced release of AA and PGE2. These findings indicate that HIV-induced TNF-alpha regulates the release of AA and PGE2, which might provide insight into the mechanisms involved in the pathogenesis of HIV-related disorders.

Protein kinase C and intracellular free Ca++: relationship to human immunodeficiency virus (HIV)-induced cellular hyporesponsiveness

Protein Kinase C (PKC) and Ca++ are both involved in the chain of events leading to T-cell activation. An impairment of the immune response is characteristic of T cells obtained from patients with HIV infection. In this report, the involvement of PKC and Ca++ in HIV-mediated cellular hyporesponsiveness was examined. Infection of peripheral blood mononuclear cells (PBMC)s from HIV-seronegative normal donors with HIV strain HTLV IIIB, or two fresh patient isolates produced a 1.4-, 10.7-, and 11.4-fold enhancement in PKC activity at 1 hr postinfection (PI) and a 1.8-, 2.3-, and 3.8-fold enhancement at 12 hr PI, respectively. A marked decrease of PKC content, as determined by Western Blot analysis, was observed in HIV-infected cells by Day 4 and 7 PI compared with mock-infected control cells. Furthermore, PKC synthesis was also inhibited in cells from immunosuppressed AIDS patients. PKC activity of PBMCs from HIV-infected patients did not change in response to 1 microM of phorbal myristate acetate (PMA). In contrast, the same dose enhanced the activity by 50%-100% in PBMCs from normal HIV-seronegative donors. A 40%, 50%, and 125% increase in intracellular free Ca++ in response to HIV infection was observed 12 hr PI in MT4, JURKAT, and PBMCs, respectively. However, the increase in intracellular free Ca++ in HIV-infected PBMCs obtained from normal donors in response to PHA was 56% and 17% compared with an increase of 100% and 120% in mock infected cells at 12 hr and 1 week PI, respectively. Comparing the Ca++ response to PHA in PBMCs from HIV-infected patients showed that patients with < 250 absolute T4 cells/mm3 had an impaired Ca++ response. These data suggest that there is a relationship between intracellular free Ca++ and PKC and HIV-induced T-cell hyporesponsiveness.

Cytomegalovirus DNA polymerase activity and an 80 kDa-associated polypeptide: a potential diagnostic tool for CMV disease

CMV has been reported to be associated with a DNA polymerase activity (DPA). In this communication its purification, characterization and potential diagnostic value were examined. CMV DNA polymerase was prepared from cell free supernatants of CMV (AD 169) infected cultures. Separation and purification of the enzyme was accomplished by column chromatography of the purified, lysed virus. CMV DPA was measured on an oligo (dT)-poly (dA) template primer. SDS-PAGE and western blot analysis under reducing conditions using an anti-CMV early antibody showed an 80 kDa protein band that was associated with the peak of polymerase activity. However, CMV isolates and CMV from urines from CMV retinitis patients immunoblotted by the same Ab revealed 140 kDa and 80 kDa bands under non-reducing and reducing conditions respectively, the latter was also associated with a 58 kDa band. The diagnostic value of the CMV associated DAP was tested using CMV positive urines. The latter demonstrated high PAA-sensitive DPA activity, compared to normal, HSV positive urines and urines from HBSAg positive patients. Taken collectively, these findings indicate the potential usefulness of CMV-associated DNA polymerase activity in the diagnosis and follow-up of patients with CMV-related illnesses.

Involvement of cAMP and protein kinase C in cytomegalovirus enhancement of human immunodeficiency virus replication

Cytomegalovirus (CMV) infection constitutes a serious threat to patients with acquired immune deficiency syndrome. Recently we reported that human immunodeficiency virus (HIV) infection of CD4+ cells was associated with sustained elevation of cellular levels of cAMP. Moreover, cyclic nucleotide modulators enhanced HIV replication by increasing intracellular levels of cAMP. In this study, the effect of CMV on HIV replication in CMV/HIV mixed infection and its relationship to cAMP were examined. MT-4 cells, CMV strain AD169, and HIV strain IIIB were used. Optimal enhancement (4.4-fold increase) of HIV replication was observed when MT-4 cells were infected with CMV at Day 0 followed by HIV on Day 4 after infection, as determined by reverse transcriptase activity on Day 11 after infection. cAMP (measured by radioimmunoassay) levels in cells infected with CMV alone, HIV alone, or CMV/HIV together were 2-, 3-, and 5-fold above untreated cells, respectively. CMV also enhanced the replication of UV-irradiated HIV 4-fold and this was associated with a 2-fold increase in cAMP as well. Moreover, UV-irradiated CMV enhanced HIV replication 8.8-fold. The same dose of viable and UV-irradiated CMV used in the above experiments increased protein kinase C activity in these cells 3.0- and 8.0-fold, respectively. These findings might suggest that cAMP and protein kinase C are involved in CMV enhancement of HIV replication. These findings may have relevance to the identification of novel target sites for development of antiviral therapeutics.

Primary intraorbital meningioma and schwannoma--a rare association

Primary intraorbital meningioma and Schwannoma are rare tumours. For them to occur concurrently, or one following soon after another should be considered a curiosity. We present a 40 year old male who reported with proptosis of the right eye and a meningioma was removed surgically. Within 3 months symptoms recurred and a schwannoma was removed at surgery from the same site. Interesting features of the lesion are presented and discussed.