Chromoblastomycosis Presenting with Sporotrichoid Distribution and Bony Destruction: A Rare Presentation

Chromoblastomycosis (CBM) presenting with linear distribution and with underlying bony destruction is rare. Herein, we report such a presentation in a farmer who presented with ulcerated nodules over the right leg and swelling of the right foot. Potassium hydroxide (KOH) preparation and histopathological examination of biopsy from nodule revealed characteristic sclerotic bodies on Gomori methenamine silver and periodic acid Schiff stain (PAS), which confirmed the diagnosis of chromoblastomycosis. X-ray of right foot revealed osteolytic destruction of right third metatarsophalangeal joint. Work-up for systemic involvement did not reveal any involvement. He was placed on combination therapy of itraconazole and terbinafine and is under follow-up.

Updates on Management of Leprosy in the Context of COVID-19 Pandemic: Recommendations by IADVL SIG Leprosy

The Special Interest Group (SIG) on leprosy thought it to be prudent to revisit its previous practice recommendations through this update. During this period, the pandemic course shifted to a 'second wave' riding on the 'delta variant'. While the number of cases increased manifold, so did the research on all aspects of the disease. Introduction of vaccination and data from various drug trials have an impact on current best practices on management of diseases including leprosy. The beneficial results of using steroids in management of COVID-19, gives elbow room regarding its usage in conditions like lepra reactions. On the other hand, the increase in cases of Mucormycosis again underlines applying due caution while recommending immunosuppressants to a patient already suffering from COVID-19. This recommendation update from SIG leprosy reflects current understanding about managing leprosy while the dynamic pandemic continues with its ebbs and flows.

Study of BCG Immunotherapy in the Management of Multiple, Extensive Non-Genital Cutaneous Common Warts

Background and Aims:

Most of the available treatment therapeutic modalities for warts are aimed at destruction of virus. However, despite adequate treatment, the virus may persist in the surrounding tissues leading to recurrence. Owing to side effects such as pain, scarring, and risk of secondary infection, these modalities may not be suitable for multiple lesions, extensive involvement and for the treatment of warts in the paediatric age group. The aim of the study was to evaluate the efficacy and safety of intra lesional BCG vaccine in the management of patients with multiple extensive non-genital common warts.

Methods:

Thirty patients with multiple, extensive non-genital cutaneous common warts, with age ranging from 6 to 60 years who were not on any treatment for warts and did not have any active infections (including HIV) or past history of tuberculosis attending the department of dermatology of our hospital in a 2-year period were included. Mantoux test was performed in all patients and positive responders were taken up for study. BCG vaccine was administered into the largest wart intradermally and the injection was repeated every 3 weeks for a maximum of five injections or till the complete clearance of warts, whichever was earlier . The efficacy was assessed every 3 weeks and a final assessment was done at the end of the 12^th week. Patients were followed up for another 6 months.

Observations:

Majority of patients were in the age group of 5-14 years. Males (63.3%) were afflicted more than females. Most patients (63.3%) exhibited partial response at the site of injected wart at the end of one month and 70% patients showed complete clearance at the end of 3 months and 36.6% responded with 3 injections and 26.6% patients required 4 for response followed 23.3% requiring 5 injections.

Conclusion:

Intralesional immunotherapy using by BCG vaccine appears to be is a promising treatment modality for the treatment of warts, particularly the multiple and recalcitrant ones. The advantages include the resolution of both the injected and distant warts with negligible recurrence and with minimal side effects.

Erythema Gyratum Repens Associated With Diffuse B-cell Lymphoma-Report of A Rare Case

Erythema gyratum repens (EGR) is a rare paraneoplastic dermatosis known to be associated with internal malignancy. Herein, we report a case of EGR with diffuse large B-cell lymphoma (DLBCL) in a young farmer who presented with generalized massive lymphadenopathy and wood-grain pattern dermatosis. Lymph node biopsy with immunohistochemistry established the diagnosis of DLBCL. He was managed by the oncologist with R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) regimen which alleviated his symptoms considerably after completion of three cycles and was under follow-up.

Zygomycosis of the Scalp Caused by Rhizopus oryzae Presenting as Kerion in an Immunocompetent Child

Deep mycosis of the scalp caused by Rhizopus oryzae mimicking kerion is rare. Herein, we report a case of such infection in a 5-year-old immunocompetent boy who presented with multiple painful boggy swellings with discharging sinuses on the scalp of 4 months’ duration. Purulent discharge from the swelling cultured on Sabouraud's dextrose agar yielded R. oryzae species which was confirmed by molecular analysis by polymerase chain reaction. The child was managed with parenteral liposomal amphotericin-B which helped in clearance of infection.

Malignant Syphilis in an Immunocompetent Adult Male

The occurrence of malignant syphilis in an immunocompetent individual is rare. We present malignant syphilis in a 35-year-old immunocompetent male who presented with a 1-month history of noduloulcerative lesions on the torso. Examination revealed multiple pustules, nodules, and deep-seated ulcers distributed on the trunk, face, and upper and lower limbs. Characteristic morphology of lesions, positive serological tests for syphilis, characteristic histopathology, and resolution of lesions following institution of penicillin therapy confirmed the clinical diagnosis of malignant syphilis.

Amelanotic Melanoma in the Vicinity of Acquired Melanocytic Nevi and not Arising from Agminated Melanocytic Nevi: Masquerading as Pyogenic Granuloma

Amelanotic melanoma (AMM) presenting as pyogenic granuloma and occurring in the vicinity of acquired melanocytic nevi is rare. Herein, we report such a manifestation in a 68-year-old male who presented with the painful red nodule and multiple pigmented patches involving the left great toe. Histopathological examination of skin biopsy taken from the nodule with an immunohistochemical study using HMB45 and S-100 confirmed the diagnosis of AMM. Biopsy from the pigmented patch near the nodule showed features of melanocytic nevus. Investigative work up revealed metastatic deposits in the left inguinal lymph node with no evidence of systemic involvement, placing him in malignant melanoma Stage IIIC of American Joint Committee on Cancer (AJCC) tumor node metastasis system. The development of AMM in the vicinity of acquired melanocytic nevi and manifesting as granuloma pyogenicum is unique in this case.

Coexistence of Solid (Nodular) and Differentiated (Adenoid) Basal Cell Carcinoma at the Same Anatomical Site

Coexistence of two different histopathological types of basal cell carcinomas (BCCs) in the same anatomical site is rare and interesting. Herein, we report a case of coexistence of nodular and adenoid BCC in a 78-year-old peasant who presented with a plaque and a globular swelling on left paranasal region of few years duration. Histopathology of skin biopsy with immunohistochemistry study using antibodies to S100, epithelial membrane antigen (EMA) and cytokeratin 7 (CK 7) from the margin of the ulcer and globular swelling confirmed the diagnosis that revealed features of nodular and adenoid basal cell carcinoma, respectively. Investigative work up did not reveal evidence of metastasis.

Bilateral Symmetrical Congenital Giant Becker's Nevus: A Rare Presentation

Becker's nevus is a focal epidermal hypermelanotic disorder. It morphologically presents as unilateral, hyperpigmented, hypertrichotic patch on upper trunk, proximal upper extremities and arms. However, Becker's nevus presenting as bilateral, symmetrical patches is rare. Herein, we report a rare case of giant Becker's nevus with bilateral symmetrical presentation in an adult male.

Unilateral Ulcerating Clear-Cell Syringomas Involving Left Groin in a Non-Diabetic Woman - Report of a Rare Presentation

Clear-cell syringomas, a rare histologic variant of syringomas, frequently coexist with diabetes mellitus. Clinically, it presents as skin colored papules distributed symmetrically around periorbital region. However, asymmetrical distribution of syringomas is rare and much rarer is the ulceration in such syringomas. Ulceration in such asymmetrical syringomas has not been reported so far. Herein, we report ulceration of clear-cell syringomas involving left groin in a middle aged non-diabetic woman.

Acquired lymphangiectasis following surgery and radiotherapy of breast cancer

Acquired lymphangiectasia (AL) is a significant and rare complication of surgery and radiotherapy. We report lymphangiectasia in a 40-year-old woman who had undergone radical mastectomy and radiotherapy. After 4 years of combined therapy, she developed multiple vesicles and bullae. Skin biopsy confirmed the diagnosis of lymphangiectasia. The case is unique as it is not associated with lymphedema, which is a usual accompaniment of lymphangiectasia following surgery and radiotherapy. AL is usually asymptomatic, but trauma may cause recurrent cellulitis. Treatment modalities include electrodessication, surgical excision, sclerotherapy and carbon dioxide laser ablation.

Pancreatic panniculitis in a child

Pancreatic panniculitis is an uncommon cause of panniculitis. It is associated with acute or chronic pancreatic disease. 1½ year old boy was referred for erythematous tender nodules involving both legs and associated with abdominal distention, fever, and vomiting. Dermatological examination revealed multiple erythematous tender nodules distributed over front and back of legs. Blood chemistry showed raised serum amylase (430 IU/ 1). Ultrasonography showed a pseudopancreatic cyst. Multislice CT scan was suggestive of a pseudopancreatic cyst. A skin biopsy showed typical features of pancreatic panniculitis which included lobular panniculitis with lipocyte degeneration with few Ghost cells.

Cryoglobulinemia in a child

Cryoglobulinemia is a rare condition. We report a case of cryoglobulinemia in 1.5-year-old boy, who presented with bluish black discoloration of hands and feet. Serum was positive for cryoglobulins. The serum cryoglobulin level was 70 μg/ml (normal <20 μg). Serum protein electrophoresis revealed the presence of M-spike. Serum immunofixation and assessment of clonality could not be done as these specialized investigations are not available here. Investigations did not reveal any systemic involvement. He was treated with anticoagulants, broad-spectrum antibiotics, and systemic steroids with which he recovered completely.

Study of leprosy in children

Leprosy, a disease as oId a mankind, has been a public health problem in many developing countries and among children, it reflects disease transmission in the community and efficiency of control programmes study on childhood leprosy was carried out Gandhi Hospital, spread over 4 years. There were 32 children among 280 diagnosed cases of leprosy. The study revealed an incidence of 11.43% among leprosy patients with more number of boy being affected than girls. Most of children presented with hypopigmented anaesthetic patches. Hansen's BT was the most common clinical type of leprosy with extremities being the common site of involvement. Slit-skin smear was positive in 25% of children. We could find significant positive clinico-pathological correlation among 12 children who were subjected to biopsy. Reactional states and deformites were less common in our study.

Multicentric reticulohistiocytosis

A 41 -year-old man presented with multiple, painful and tender nodules on the palms, soles, scalp; and on the limbs predominantly around the joints with associated arthropathies. Smaller nodules were seen on the ear helices. There was no other clinically evident or investigative abnormality. Histopathological study confirmed a diagnosis of multicentric reticulo histiocytosis.

Effects of a potato cysteine proteinase inhibitor on midgut proteolytic enzyme activity and growth of the southern corn rootworm, Diabrotica undecimpunctata howardi (Coleoptera: Chrysomelidae)

The major proteinase activity in extracts of larval midguts from the southern corn rootworm (SCR), Diabrotica undecimpunctata howardi, was identified as a cysteine proteinase that prefers substrates containing an arginine residue in the P1 position. Gelatin-zymogram analysis of the midgut proteinases indicated that the artificial diet-fed SCR, corn root-fed SCR, and root-fed western corn rootworms (Diabrotica virgifera virgifera) possess a single major proteinase with an apparent molecular mass of 25kDa and several minor proteinases. Similar proteinase activity pH profiles were exhibited by root-fed and diet-fed rootworms with the optimal activity being slightly acidic. Rootworm larvae reared on corn roots exhibited significantly less caseinolytic activity than those reared on the artificial diet. Midgut proteolytic activity from SCR was most sensitive to inhibition by inhibitors of cysteine proteinases. Furthermore, rootworm proteinase activity was particularly sensitive to inhibition by a commercial protein preparation from potato tubers (PIN-II). One of the proteins, potato cysteine proteinase inhibitor-10', PCPI-10', obtained from PIN-II by ion-exchange chromatography, was the major source of inhibitory activity against rootworm proteinase activity. PCPI-10' and E-64 were of comparable potency as inhibitors of southern corn rootworm proteinase activity (IC(50) =31 and 35nM, respectively) and substantially more effective than chicken egg white cystatin (IC(50) =121nM). Incorporation of PCPI-10' into the diet of SCR larvae in feeding trials resulted in a significant increase in mortality and growth inhibition. We suggest that expression of inhibitors such as PCPI-10' by transgenic corn plants in the field is a potentially attractive method of host plant resistance to these Diabrotica species.

Rapid gastric fluid digestion and biochemical characterization of engineered proteins enriched in essential amino acids

The barley high lysine (BHL) proteins are nutritionally enhanced derivatives of barley chymotrypsin inhibitor-2 (CI-2). A compactly folded new CI-2 derivative, BHL9, was engineered with the highest content of threonine, tryptophan, and isoleucine yet achieved in this protein family (15.1, 9.4, and 12.1 wt %, respectively). BHL9 had an unfolding midpoint of 5.5 M guanidinium chloride, significantly greater than values for wild type (3.9 M) or for the previously most stable BHL protein, BHL8 (3.6 M). BHL9 and all other derivatives were digested within 15 s in simulated gastric fluid (SGF), suggesting nutritional availability upon ingestion. Denaturation of the proteins in SGF minus pepsin was revealed by changes in their fluorescence emission spectra and/or far UV circular dichroism spectra. The proteins lack homology to known allergens. Significantly, the BHL8 and BHL9 proteins were stable to proteases at pH 7.5 or 8.0, attesting to their potential for high expression in plants.

Strategies to generate antibodies capable of distinguishing between proteins with >90% amino acid identity

Protein engineering is a common strategy for the generation of protein variants with new properties. The engineered variants often have a high degree of similarity with the wild-type progenitor protein, necessitating a tool (e.g., antibody) to distinguish the wild-type and variant protein forms. As part of an overall effort to understand the process of incorporation of amino acids into storage proteins during seed fill in soybean, we have engineered a variant of soybean vegetative storage protein beta (VSPbeta) that is 91.8% identical in amino acid sequence to the wild-type protein, but contains 10% methionine (VSPbeta-Met, unpublished results). Thus, it would be desirable to have antibodies that specifically recognize VSPbeta-Met over the endogenously expressed wild-type protein in transgenic plants. To this end, we compared three strategies for the isolation of VSPbeta-Met-specific antibodies: (1) hybridoma production using VSPbeta-Met protein as the antigen, (2) polyclonal antibody production in rabbits using a peptide antigen corresponding to a methionine-rich region of VSPbeta-Met, and (3) subtractive immunization in mice using VSPbeta-WT as the tolerogen, cyclophosphamide for immunosuppression and VSPbeta-Met as the immunogen. While the first strategy generated antibodies cross-reactive to both antigens, the second strategy generated polyclonal antibodies that preferentially recognized the variant protein in immunoblots. However, using subtractive immunization, we were able to generate mouse polyclonal antibodies that exhibited 10-fold greater reactivity with VSPbeta-Met than VSPbeta-WT in an ELISA.

A single disulfide bond restores thermodynamic and proteolytic stability to an extensively mutated protein

The potential for engineering stable proteins with multiple amino acid substitutions was explored. Eleven lysine, five methionine, two tryptophan, one glycine, and three threonine substitutions were simultaneously made in barley chymotrypsin inhibitor-2 (CI-2) to substantially improve the essential amino acid content of the protein. These substitutions were chosen based on the three-dimensional structure of CI-2 and an alignment of homologous sequences. The initial engineered protein folded into a wild-type-like structure, but had a free energy of unfolding of only 2.2 kcal/mol, considerably less than the wild-type value of 7.5 kcal/mol. Restoration of the lysine mutation at position 67 to the wild-type arginine increased the free energy of unfolding to 3.1 kcal/mol. Subsequent cysteine substitutions at positions 22 and 82 resulted in disulfide bond formation and a protein with nearly wild-type thermodynamic stability (7.0 kcal/mol). None of the engineered proteins retained inhibitory activity against chymotrypsin or elastase, and all had substantially reduced inhibitory activity against subtilisin. The proteolytic stabilities of the proteins correlated with their thermodynamic stabilities. Reduction of the disulfide bond resulted in substantial loss of both thermodynamic and proteolytic stabilities, confirming that the disulfide bond, and not merely the cysteine substitutions, was responsible for the increased stability. We conclude that it is possible to replace over a third of the residues in CI-2 with minimal disruption of stability and structural integrity.

Involvement of cysteine residues and domain interactions in the reversible unfolding of lipoxygenase-1

Urea-induced unfolding of lipoxygenase-1 (LOX1) at pH 7.0 was followed by enzyme activity, spectroscopic measurements, and limited proteolysis experiments. Complete unfolding of LOX1 in 9 M urea in the presence of thiol reducing or thiol modifying reagents was observed. The aggregation and oxidative reactions prevented the reversible unfolding of the molecule. The loss of enzyme activity was much earlier than the structural loss of the molecule during the course of unfolding, with the midpoint concentrations being 4.5 and 7.0 M for activity and spectroscopic measurements, respectively. The equilibrium unfolding transition could be adequately fitted to a three-state, two-step model (N left arrow over right arrow I left arrow over right arrow U) and the intermediate fraction was maximally populated at 6.3 M urea. The free energy change (DeltaG(H(2)O)) for the unfolding of native (N) to intermediate (I) was 14.2 +/- 0.28 kcal/mol and for the intermediate to the unfolded state (U) was 11.9 +/- 0.12 kcal/mol. The ANS binding measurements as a function of urea concentration indicated that the maximum binding of ANS was in 6.3 M urea due to the exposure of hydrophobic groups; this intermediate showed significant amount of tertiary structure and retained nearly 60% of secondary structure. The limited proteolysis measurements showed that the initiation of unfolding was from the C-terminal domain. Thus, the stable intermediate observed could be the C-terminal domain unfolded with exposed hydrophobic domain-domain interface. Limited proteolysis experiments during refolding process suggested that the intermediate refolded prior to completely unfolded LOX1. These results confirmed the role of cysteine residues and domain-domain interactions in the reversible unfolding of LOX1. This is the first report of the reversible unfolding of a very large monomeric, multi-domain protein, which also has a prosthetic group.

Conformation and stability of barley chymotrypsin inhibitor-2 (CI-2) mutants containing multiple lysine substitutions

A major goal of agricultural biotechnology is to increase the nutritional value of maize seed through the expression of heterologous proteins enriched in lysine. One promising candidate is barley chymotrypsin inhibitor-2 (CI-2), a plant protein that has been extensively characterized with respect to structure and function. Based on the tertiary structure of wild-type (WT) CI-2, five mutants with lysine contents ranging from 20 to 25 mol percent were designed, expressed in Escherichia coli and purified by ion exchange and gel permeation chromatography. Inasmuch as previous transgenic experiments suggested that proper folding and stability may be essential for in vivo accumulation of the engineered proteins in plant cells, we first undertook an in vitro study of the conformation and thermodynamic stability of the CI-2 mutants in order to select an ideal candidate for plant expression. Mutant and WT CI-2 proteins had similar circular dichroism spectra, suggesting similar secondary structures. However, differences in the accessibility of the sole tryptophan residue, Trp24, indicated that the local conformation differed among the mutants. The thermodynamic stability of the mutants ranged from <2 to 4.9 kcal/mol compared with approximately 7 kcal/mol for the wild-type protein. In conjunction with proteolytic stability studies, we have identified one mutant that has the potential to be expressed in a stable manner in plant cells.

Affinity properties of phosvitin: interaction of phosvitin with serine hydroxymethyl transferase

The affinity of phosvitin with serine hydroxymethyl transferase (SHMT), an acidic multi-subunit protein, was evaluated by measurements of enzyme activity, sedimentation velocity, steady-state fluorescence, circular dichroism and kinetic thermal stability. While the presence of phosvitin had no effect on the SHMT activity, the sedimentation coefficient of SHMT increased from 8.7 S to 12.5 S suggesting the formation of a complex at a SHMT:phosvitin molar ratio of 2:1. Based on steady-state fluorescence quenching measurements an association constant of 2.4 +/- 0.2 x 10(5) M-1 at 25 degrees C was obtained for the interaction of phosvitin with SHMT. The temperature dependency of the association constant in the range 15-35 degrees C suggests the involvement of ionic forces in the interaction. The thermal inactivation of SHMT followed first order kinetics. In the presence of phosvitin the rate constant decreased and half time increased. The circular dichroism measurements suggest that phosvitin interaction does not involve pyridoxal phosphate binding domain of the enzyme. Although minor changes in the secondary structure of the enzyme were observed, the environment around aromatic amino acids did not change significantly.

Conformation and antimicrobial activity of linear derivatives of tachyplesin lacking disulfide bonds

Tachyplesin is a potent antimicrobial peptide isolated from the hemocytes of the horseshoe crab, Tachypleus tridentatus. Previous studies have shown that the 17-residue peptide has an intrinsic amphipathic structure conferred by two antiparallel beta-sheets held rigidly by two disulfide bonds. Taking its short length into account and the potential of such a small polypeptide to take on multiple conformational states, one may assume that the disulfide bonds are relevant determinants of function. However, in order to gain a global perspective on the tolerance of cysteine residues in tachyplesin to amino acid substitutions, a series of linear peptides have been synthesized and their physicochemical properties analyzed. In these linear peptides, the cysteines have been replaced with amino acids possessing different side-chain properties, i.e., aliphatic hydrophobic (Ala, Leu, Ile, Val, and Met), aromatic hydrophobic (Phe and Tyr), and acidic (Asp). Activity assays using natural and synthetic membranes, and conformational measurements, highlight the subtle influence and variability of the amino acid side-chain properties on peptide structure. While an unequivocal interpretation of the results will have to await more refined structural measurements, our results indicate that a rigidly held disulfide-bonded beta-pleated sheet structure may not be absolutely essential for antimicrobial activity. Furthermore, the results challenge the accepted dogma of structure-activity relationships among antimicrobial peptides and suggest that the maintenance of peptide hydrophobic-hydrophilic balance may be a critical parameter, in addition to structure, in the design of peptides with pharmaceutical relevance.

Conformation of polygalacturonase-II from Aspergillus carbonarius--a spectroscopic study

Solution conformation of polygalacturonase from Aspergillus carbonarius was determined by spectroscopy. UV absorption, second derivative, near-UV CD, fluorescence emission spectra and fluorescence quenching measurements suggest that the tryptophan fluorophores are in a hydrophobic environment. Of the nine tryptophan residues, only one is exposed to the solvent. In the near UV region the enzyme exhibits very weak CD bands, the far UV CD spectrum has a minimum at 218 nm; the enzyme is rich in parallel beta structure. Modification of solvent exposed tryptophan by N-bromosuccinimide resulted in the complete loss of enzyme activity. The enzyme is very sensitive towards urea induced unfolding, with complete loss of activity at 3 M urea concentration.

Rapid method to separate the domains of soybean lipoxygenase-1: identification of the interdomain interactions

Lipoxygenase-1 (LOX1) from soybeans was cleaved with chymotrypsin (Ramachandran et al., 31 (1992) 7700-7706). The domains were separated on a Sephadex G-50 column by minimising domain interactions at pH 4.0. The molecular weight and apparent homogeneity of the domains were established by SDS-PAGE. The solution conformation of the 60 kDa and 30 kDa fragments was compared with that of native LOX1. 1-Anilino-8-naphthalene sulphonate (ANS) binding measurements confirmed the exposure of large hydrophobic residues on the surface of the 60 kDa due to separation of the domains. The monomeric nature of the 60 kDa fragment was confirmed by HPLC gel filtration. The increased number of binding sites and magnitude of binding constant suggested the involvement of extensive hydrophobic interactions between the two domains. The essential cofactor iron was with the C-terminal domain. The attempts to resolve and reconstitute the catalytic activity of isolated domains were not successful.

The detection of kinetic intermediates during the unfolding of lipoxygenase-1 by urea or guanidine hydrochloride

The unfolding of lipoxygenase-1 by urea and guanidine hydrochloride has been followed at the optimum pH of enzyme activity. The unfolding of lipoxygenase-1 by urea or guanidine hydrochloride was characterized by equilibrium transition curves for different parameters like (i) enzyme activity, (ii) change in ellipticity values at 222 nm, and (iii) relative fluorescence intensity at 332 nm could not be superimposed. The transition curves displayed more than one plateau region suggesting the presence of stable intermediates during unfolding. At urea concentrations less than 1 M there was no significant loss in activity although loss in secondary structure was approximately 20%. At 4.0 M urea concentration there was complete loss of activity with a midpoint concentration of 2.5 M urea. The loss in secondary structure was biphasic. The first transition had a midpoint concentration of 1.2 M, while the second transition which was complete at 8.0 M urea had a midpoint concentration of 3.5 M urea. The changes in relative fluorescence intensity and shift in emission maximum were complete at 8.0 M urea. The Stern-Volmer constant for acrylamide and potassium iodide did not change at urea concentrations less than 4 M and then at higher concentrations increased. The reactivity of sulfhydryl groups to Ellman's reagent increased during the course of unfolding. The kinetics of unfolding supported the presence of stable intermediates during unfolding. The unfolding was irreversible and complex because of the multidomain nature. The apparent irreversibility could be related to aggregation during unfolding which precluded the determination of thermodynamic parameters.

In vitro activity of the antimicrobial peptides human and rabbit defensins and porcine leukocyte protegrin against Mycobacterium tuberculosis

Three independent assay methods were used to investigate the activities of antimicrobial peptides (human and rabbit defensins and protegrin from porcine leukocytes) against Mycobacterium tuberculosis in vitro. M. tuberculosis H37Ra was cultured in the presence of human neutrophil peptide 1, synthetic rabbit neutrophil peptide 1, or porcine protegrin 1 at 37 degrees C for 6 to 48 h, and antimycobacterial activity was measured by CFU assay. These peptides at a concentration of 50 microg/ml showed significant antibacterial effects on M. tuberculosis after 24 and 48 h of incubation (85.9 to 97.5% at 24 h and 91.6 to 99.4% at 48 h). A radiometric method and a radial diffusion assay confirmed these observations. Antibacterial activity against M. tuberculosis was independent of calcium (1.0 mM) or magnesium (1.0 mM) and not inhibited by sodium chloride (100 mM). The optimal pH for antibacterial activity against M. tuberculosis was greater than 4.0. Three clinical isolates of M. tuberculosis were also studied, and these peptides showed 86.3 to 99.0% reduction in CFU of these organisms. Morphological studies using scanning electron microscopy showed that defensins caused lesions on the surface of H37Ra. These observations suggest that antimicrobial peptides such as defensins and protegrins may represent an important component of the host defense mechanism against M. tuberculosis and offer a potential new approach to therapy.

Role of disulfide linkages in structure and activity of proteinase inhibitor from horsegram (Dolichos biflorus)

Proteinase inhibitor isolated from horsegram (Dolichos biflorus or Macrotyloma uniflorum) inhibited specifically the enzymes trypsin and chymotrypsin. The inhibitor contained seven disulfide linkages and was free from thiol groups. The inhibitor is resistant to denaturation by urea, guanidine hydrochloride or sodium dodecyl sulfate. Reduction of the inhibitor with dithiothreitol abolished both trypsin and chymotrypsin inhibitory activities. The kinetic plots of the reduction as followed by activity and loss in structure as reflected in the 257 nm CD band could be superposed; loss in the activity paralleled the loss in structure. The kinetics of the reduction process was complex; reduction of the inhibitor was slow and depended on the concentration of DTT. Reduction of the disulfide linkages with DTT affected the tertiary structure significantly and secondary structure was not affected considerably. Fluorescence quenching by acrylamide and potassium iodide suggested the unfolding of the molecule due to reduction. Thus, disulfide linkages play a predominant role in maintaining the three-dimensional structure of the inhibitor.

Design and synthesis of amphipathic antimicrobial peptides

A large proportion of antimicrobial peptides share a common structural feature that is critical to their antimicrobial activity, i.e. amphipathic alpha-helices. The amphipathy of a polypeptide chain can be quantitated through the value of the hydrophobic moment. Generally, antimicrobial peptides are characterized by high hydrophobic moment and low hydrophobicity values. Using these criteria we have identified two short segments that possess hydrophobic moment properties associated with known antimicrobial peptides. Using in vitro assays the segment derived from the protein perforin displays no antifungal or antibacterial activity and, while showing no alpha-helicity in buffer or liposomes, exhibits a modest degree of alpha-helical structure in the presence of the alpha-helical inducer, 2,2,2-trifluoroethanol. However, rational modifications result in a derivative which assumes an alpha-helical conformation in the presence of liposomes, exhibits potent antifungal activity against plant fungal pathogens, has significant antibacterial activity, effects leakage of a fluorescent dye from acidic liposomes and is devoid of hemolytic activity. Results are also presented for a segment derived from the human immunodeficiency virus envelope protein. We suggest that the identification of putative amphipathic structures in proteins may provide a useful starting strategy in the design and synthesis of antimicrobial peptides.

Structure-function validation of high lysine analogs of alpha-hordothionin designed by protein modeling

Cereal grains and legume seeds, which are key protein sources for the vegetarian diet, are generally deficient in essential amino acids. Maize, in particular, is deficient in lysine. The inherent lack of lysine-rich proteins in maize has necessitated the search for heterologous proteins enriched in this amino acid, the isolation of the corresponding gene and its ultimate introduction into maize through plant transformation techniques. However, a rate-limiting step to this strategy has been the availability of plant-derived lysine-rich proteins. An appealing solution to the problem is to artificially increase the lysine content of a given protein by mutating appropriate residues to lysine. Here, we expound this strategy, starting with the protein alpha-hordothionin that is derived from barley seeds and consists of five lysine residues in a total of 45 amino acids (11% lysine). To facilitate rational substitutions, the 3-D structure of the protein has been determined by homology modeling with crambin. Based on this model, we have identified surface residues amenable to substitution with lysine. Furthermore, the acceptability of the mutations has been validated through the synthesis and characterization of the derivatives. To this end, our approach has permitted the creation of a modified alpha-hordothionin protein that has a lysine content of approximately 27% and retains the antifungal activity of the wild-type protein.

Characterization of the lectin from the bulbs of Eranthis hyemalis (winter aconite) as an inhibitor of protein synthesis

The lectin from Eranthis hyemalis has been previously characterized as consisting of two polypeptide chains covalently linked by disulfide bond(s) (Cammue, B. P., Peeters, B., and Peumans, W. J. (1985) Biochem. J. 227, 949-955). We have further characterized the biochemical properties of the lectin and demonstrated that it possesses the property of inhibition of protein synthesis using in vitro eukaryotic translation systems. The protein also possesses antiviral activity against the plant virus, alfalfa mosaic virus, and larvicidal activity against the southern corn rootworm, Diabrotica undecimpunctata howardii, a major insect pest of the maize plant. Both isoelectric focusing on gels and chromatofocusing indicated heterogeneity of the protein, with three species having isoelectric points in the range 4-5. The disulfide bond(s) can be rapidly reduced with beta-mercaptoethanol under native conditions. The reduced alkylated polypeptide chains remain associated under native conditions to form a species, EHL', that elutes at the same position as the native protein and has the same molecular weight by sedimentation equilibrium experiments. However, circular dichroism and fluorescence measurements indicated conformational differences between the species.

Synthesis and characterization of defensin NP-1

Defensins are a group of small, cationic, antimicrobial proteins found in the cytoplasmic granules of neutrophils and macrophages of a variety of mammalian species. One such defensin, NP-1, isolated from rabbit neutrophils, has been shown to consist of 33 amino acids rich in arginine and cysteine residues. We have synthesized NP-1 on an Applied Biosystems Model 431A peptide synthesizer using FastMoc chemistry involving HBtu [2-1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate] activation for coupling amino acids. The linear peptide was folded by air oxidation to the biologically active form containing three disulfide bonds and purified by reverse phase chromatography. The amino acid sequence of the synthetic peptide was confirmed by Edman degradation. Molecular weight determination by plasma desorption mass spectroscopy (PDMS) gave a value of 3898.6, in agreement with the expected molecular weight of 3898. The biological activity of the synthetic peptide, as measured by its antifungal activity against several pathogenic fungi, was indistinguishable from that of the natural NP-1. Also, the CD spectrum was equivalent to that of natural NP-1, indicating conformational identity of the two species.

Purification and characterization of a novel antimicrobial peptide from maize (Zea mays L.) kernels

Several small, acid-soluble, basic peptides with anti-microbial properties have been isolated from maize (inbred B73) kernels. One of these peptides (MBP-1) has been purified to homogeneity and characterized. The peptide has a molecular weight of 4127.08 as determined by plasma desorption mass spectroscopy, has no free cysteines, and is predominantly alpha-helical as determined by circular dichroism. The primary sequence of the peptide (33 residues) has been determined by Edman degradation and shows no homology to the thionins, a group of cysteine-rich peptides found in some cereals including wheat, barley, and sorghum, as well as several dicot species. Like the thionins, however, MBP-1 has been found to have antimicrobial properties in vitro. MBP-1 inhibits spore germination or hyphal elongation of several plant pathogenic fungi, including two seed pathogens of maize (Fusarium moniliforme Sheld. and Fusarium graminearum (Gibberella zeae (Schw.) Petsch)), and several bacteria, including a bacterial pathogen of maize (Clavibacter michiganense ssp. nebraskense). A synthetic MBP-1 peptide, air-oxidized and purified by reverse phase chromatography, was equally antifungal as compared with the naturally occurring peptide.

A stoichiometric analysis of bovine serum albumin-gossypol interactions: a fluorescence quenching study

The interaction of gossypol with bovine serum albumin, human serum albumin and n-bromosuccinimide-modified bovine serum albumin has been followed by fluorescence quenching measurements. The presence of a high affinity site (association constant K = 2.2 x 10(6) M-1) for gossypol on bovine serum albumin and human serum albumin is indicated. The stoichiometry of binding for the high affinity site was evaluated using Job's method of continuous variation, thereby suggesting the formation of 1:1 complex. Modification of the tryptophan residues on bovine serum albumin does not affect the binding of gossypol to either high or low affinity site of albumin.

Interactions of methoxyamine with pyridoxal-5'-phosphate-Schiff's base at the active site of sheep liver serine hydroxymethyltransferase

The mechanism of interaction of methoxyamine with sheep liver serine hydroxymethyltransferase (EC 2.1.2.1) (SHMT) was established by measuring changes in enzyme activity, visible absorption spectra, circular dichroism and fluorescence, and by evaluating the rate constant by stopped-flow spectrophotometry. Methoxyamine can be considered as the smallest substituted aminooxy derivative of hydroxylamine. It was a reversible noncompetitive inhibitor (Ki = 25 microM) of SHMT similar to O-amino-D-serine. Like in the interaction of O-amino-D-serine and aminooxyacetic acid, the first step in the reaction was very fast. This was evident by the rapid disappearance of the enzyme-Schiff base absorbance at 425 nm with a rate constant of 1.3 x 10(3) M-1 sec-1 and CD intensity at 430 nm. Concomitantly, there was an increase in absorbance at 388 nm (intermediate I). The next step in the reaction was the unimolecular conversion (1.1 x 10(-3) sec-1) of this intermediate to the final oxime absorbing at 325 nm. The identity of the oxime was established by its characteristic fluorescence emission at 460 nm when excited at 360 nm and by high performance liquid chromatography. These results highlight the specificity in interactions of aminooxy compounds with sheep liver serine hydroxymethyltransferase and that the carboxyl group of the inhibitors enhances the rate of the initial interaction with the enzyme.

Structural and functional changes associated with cyanogen bromide treatment of wheat germ agglutinin

The lectin, wheat germ agglutinin (WGA), has been shown to have a significant larvicidal effect on the European corn borer, a major insect pest of corn. In order to characterize this toxic effect, we have undertaken structure-function studies on WGA. To this extent, the effect of cyanogen bromide (CNBr) on the conformation, subunit interactions, and biological activity of WGA has been investigated. The CNBr-modified lectin exhibits no toxicity to the ECB, cannot dimerize, does not bind to N-acetylglucosamine or its polymers, has no or vastly reduced hemagglutinating activity against red blood cells of different animals, and shows loss of an antigenic determinant by immunodiffusion. The CD spectrum of CNBr-WGA is not significantly different from that of native WGA, although the intrinsic fluorescence shows about 30% quenching. Our results suggest that the integrity of the N-terminal domain of WGA is essential for dimer formation. Furthermore, toxicity of WGA to ECB may be intrinsically related to its ability to dimerize and bind to sugar residues.

An immunoaffinity immobilized enzyme assay for neomycin phosphotransferase II in crude cell extracts

An immunoaffinity immobilized enzyme assay for neomycin phosphotransferase II (NPT II) has been developed. This method combines affinity purification with an enzyme-catalyzed reaction. The assay is mechanically simple and can be semiautomatable since all steps are performed in a microtiter plate. An immunoaffinity step separates NPT II from endogenous kinases, which may produce false positive results, and from endogenous phosphatases and inhibitors, which decrease the apparent NPT activity. This method thus exploits two modes of specificity: antigen-antibody specificity and enzyme catalysis specificity. This gives a high degree of specificity and allows quantitation of 0.1 ppm NPT in crude plant protein extracts. The catalytic ability of the NPT is not significantly hampered by its attachment to the gel, in the Km values for ATP and neomycin and the catalytic number for immobilized NPT are comparable to those for the NPT in solution.

A fluorometric study of the interaction of bradykinin with lipids

The interaction of bradykinin (BK) with lipids has been followed by steady-state fluorescence measurements. Addition of either cerebroside sulfate (CS) or phosphatidylinositol (PI), solubilized with the nonionic surfactant C12E8, to BK or its analogue [Gly6]-BK enhances the relative fluorescence intensity of peptide emission at 288 nm. Fluorometric titration of the peptide with lipid has been used to quantitate the interactions in terms of stoichiometry and equilibrium constant. Job's method of continuous variation for the BK-CS interaction gave a stoichiometry of 1:2 for the complex. The value of the equilibrium constant, K, for the interaction of either BK or [Gly6]-BK with CS is 1.5.10(4) M-1. The BK-PI interaction is weaker; K = 5.0.10(3) M-1. Although electrostatic forces no doubt play a major role in these interactions, measurements on the model peptide Gly-Phe-Gly indicate that the phenylalanine residues of BK are disposed in the hydrophobic environment provided by the lipid-C12E8 mixed micelle. 13C-NMR measurements on [99% 13C alpha-Gly6]-BK show that there is no change in its cis/trans ratio upon interaction with CS. The increase in the relative fluorescence intensity of BK accompanying its cooperative interaction with sodium dodecyl sulfate (SDS) implicates the role of hydrophobic forces in this interaction as well. These results bear on the interpretation of the changes in circular dichroism (CD) of BK caused by SDS.