Construction and expression of recombinant plasmids encoding type 1 or D-mannose-resistant pili from a urinary tract infection Escherichia coli isolate

Isolates of Escherichia coli from human urinary tract infections frequently express adherence properties found less often among normal intestinal isolates. These properties include adherence to human uroepithelial cells and primary monkey kidney cells, as well as D-mannose-resistant hemagglutination of human erythrocytes, and they are mediated by a pilus type different from type 1. The genes encoding this pilus type (pyelonephritis-associated pili, pap) and those encoding type 1 pili have been cloned from a urinary tract infection isolate of E. coli and transferred to an E. coli K-12 derivative. The recombinant plasmids were found to express functional pili and to endow the new host with all of the adherence properties of the urinary tract infection isolate. Both pilus types were found to be genetically distinct, and unlike the adherence genes from bovine, porcine, and human diarrheal isolates, both were found to be chromosomally encoded.

HIV-1 genotypic resistance patterns predict response to saquinavir-ritonavir therapy in patients in whom previous protease inhibitor therapy had failed

BACKGROUND

Tests for resistance to HIV drugs are available for clinical use; however, their predictive value has not been fully assessed.

OBJECTIVES

To determine HIV-1 genotypic predictors of a virologic response to saquinavir-ritonavir therapy in patients in whom at least one previous protease inhibitor-containing regimen had failed and to compare the predictive value of baseline genotype with that of standard clinical evaluation.

DESIGN

Retrospective clinical cohort study.

SETTING

University-based HIV clinic.

PATIENTS

54 HIV-1-infected adults treated with saquinavir-ritonavir who had experienced virologic failure while receiving a protease inhibitor-containing regimen for at least 3 months.

MEASUREMENTS

HIV-1 reverse transcriptase and protease gene sequences, CD4 cell counts, clinical characteristics, detailed antiretroviral treatment history, and plasma HIV-1 RNA levels at baseline and at three follow-up time points (median, 4, 12, and 26 weeks). Virologic failure was defined as a plasma HIV RNA level greater than 1000 copies/mL.

RESULTS

In 22 patients (41%), a plasma HIV-1 RNA level less than 500 copies/mL was achieved by week 12; in 15 patients (28%), this response was maintained through week 26. Clinical characteristics predicting a poorer response included a diagnosis of AIDS, lower CD4 cell count, and higher plasma HIV RNA level (P<0.03). Number of previous nucleoside reverse transcriptase inhibitors, previous protease inhibitor therapy, and duration of previous protease inhibitor therapy were predictors of poorer response (P<0.01). Multivariate regression models revealed that protease mutations present at the initiation of saquinavir-ritonavir therapy were the strongest predictors of virologic response. A model of clinical features explained up to 45% of the variation in virologic outcomes by week 12, whereas the explained variance was 71% when genotypic predictors were included.

CONCLUSIONS

In patients in whom protease inhibitor-containing antiretroviral therapy fails, HIV-1 genotype is predictive of virologic response to subsequent therapy. This predictive capacity adds to that of standard clinical evaluation.

Temperature sensitive simian virus 40 large T antigen immortalization of murine odontoblast cell cultures: establishment of clonal odontoblast cell line

During tooth formation instructive epithelial-mesenchymal interactions result in the cytodifferentiation of ectomesenchymal cells into odontoblasts which produce the dentin extracellular matrix (DECM). The purpose of our study was to establish a stable murine odontoblast cell line by immortalization of odontoblasts using retrovirus transfection. In order to accomplish this goal, we utilized a previously characterized odontoblast monolayer cell culture system supportive of odontoblast cytodifferentiation from dental papilla mesenchyme (DPM), expression and secretion of a DECM and dentin biomineralization. First mandibular molars from E-18 Swiss Webster mice were dissected, the DPM isolated, and pulp cells dissociated. Pulp cells (5 x 10(5)/well) were plated as monolayers and grown in alpha-MEM supplemented with 10% FCS, 100 units/ml penicillin and streptomycin, 50 micrograms/ml ascorbic acid. Cultures were maintained for 6 days at 37 degrees C in a humidified atmosphere of 95% air and 5% CO2, with media changes every two days. Immortalization was performed using a recombinant defective retrovirus containing the temperature sensitive SV-40 large T antigen cDNA and the neomycin (G418) resistance gene recovered from CRE packaging cells. Cultures were infected for 24 h with CRE conditioned medium containing 8 micrograms/ml of polybrene, the media was replaced with selective media containing 300 micrograms/ml of G418, and the cultures incubated at 33 degrees C for one month with media changes every 3-5 days. Neomycin resistant cells were cloned by serial dilution to single cells in 96-well culture plates and grown in selection medium at 33 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of biased amino acid substitution patterns in human immunodeficiency virus type 1 isolates from patients treated with protease inhibitors

Human immunodeficiency virus type 1 (HIV-1) amino acid substitutions observed during antiretroviral drug therapy may be caused by drug selection, non-drug-related evolution, or sampling error introduced by the sequencing process. We analyzed HIV-1 sequences from 371 untreated patients and from 178 patients receiving a single protease inhibitor. Amino acid substitution patterns during treatment were compared with inferred substitution patterns arising evolutionarily without treatment. Our results suggest that most treatment-associated amino acid substitutions are caused by selective drug pressure, including substitutions not previously associated with drug resistance.

Therapeutic uses of recombinant complement protein inhibitors

In conclusion, it is apparent that researchers are poised at the threshold of developing inhibitors of complement activation from the molecules in the RCA family. By creating soluble forms of these protective proteins for in vivo administration, or by making transgenic animals expressing these proteins or their derivatives, it may be possible to inhibit complement-mediated pathology stemming from autoimmune disease, reperfusion injuries, and physical trauma. This technology combined with current attempts to protect allografts from cellular rejection with monoclonal antibodies against members of the integrin family of adhesion molecules [52] makes it possible that the excessive mortality due to the severe shortage of human donor organs could be overcome by the use of xenografts.

Basic fibroblast growth factor and fibroblast growth factor receptors in adult olfactory epithelium

Basic fibroblast growth factor (FGF2) stimulates proliferation of the globose basal cells, the neuronal precursor in the olfactory epithelium. The present study investigates the expression of basic fibroblast growth factor and fibroblast growth factor receptors in the adult olfactory epithelium. FGF2 immunoreactivity was expressed widely in the olfactory epithelium, with the highest density of immunoreactivity in the supporting cells. In contrast, most cells in the epithelium expressed FGF2 mRNA. Fibroblast growth factor receptor-1 (FGFr1) immunoreactivity was densest in the basal cell and neuronal layers of the olfactory epithelium and on the apical surface of supporting cells. In the lamina propria FGF2 immunoreactivity and mRNA were densest in cells close to the olfactory nerve bundles. FGFr1 immunoreactivity was heaviest on the olfactory ensheathing cells. Using reverse transcriptase-polymerase chain reaction analysis, the olfactory epithelium was shown to express only three receptor splice variants, including one (FGFr1c) with which basic fibroblast growth factor has high affinity. Other receptor splice variants were present in the lamina propria. Taken together, these observations indicate endogenous sources of FGF2 within the olfactory epithelium and lamina propria and suggest autocrine and paracrine pathways via which FGF2 might regulate olfactory neurogenesis. The observation of only three receptor splice variants in the olfactory epithelium limits the members of the fibroblast growth factor family which could act in the olfactory epithelium. The widespread distribution of receptors suggests that fibroblast growth factors may have roles other than proliferation of globose basal cells.

Indomethacin-induced renal dysfunction in patients with well-compensated cirrhosis

BACKGROUND

Patients with cirrhosis and ascites are especially sensitive to the adverse renal effects of indomethacin-induced inhibition of prostaglandin synthesis. The aim of this study was to determine whether indomethacin affects renal function in patients with well-compensated cirrhosis.

METHODS

Clearance techniques were used to assess renal hemodynamics and sodium and water homeostasis.

RESULTS

The oral administration of 50 mg of indomethacin to well-compensated patients with alcoholic cirrhosis was followed by a significant decrease in glomerular filtration rate (GFR) and effective renal plasma flow because of a preferential increase in afferent arteriolar tone. Indomethacin was both antidiuretic and antinatriuretic due principally to decreased free water clearance and increased proximal tubular reabsorption of sodium. The acute changes in renal function were not sustained. Patients with a high basal GFR were particularly sensitive to the adverse renal effects of indomethacin.

CONCLUSIONS

This study indicates that in patients with well-compensated cirrhosis renal prostaglandins are functionally active and may contribute to the pathogenesis of glomerular hyperfiltration. Nonsteroidal anti-inflammatory drugs should be used with caution in all patients with cirrhosis.

Personal history, training, and worksite as predictors of back pain of nurses

Back pain among nurses is a common problem. Prior studies of this problem have been based on cross-sectional or retrospective data. This 18-month prospective study involving nurses newly graduated from nursing school investigated personal, worksite, and training factors associated with future risk of back pain. Each nurse underwent a preliminary interview and periodic follow-ups to identify those with back injuries. Contingency tables and logistic regression analyses demonstrated that prior significant back pain episodes (evidenced by previous job changes because of back pain, frequent medication use, etc.) were associated with increased future risk. Training at nursing school or on the job did not have a protective effect. This pilot study therefore suggests factors useful in placement and counseling of new nurses and indicates the need for further implementation of mechanical lift assist device use.

Is the central dogma of flow cytometry true: that fluorescence intensity is proportional to cellular dye content?

Measurements and theoretical calculations of fluorescent emission from four samples of polystyrene microspheres (diameter 0.92, 1.63, 1.90 and 4.18 microns) containing the same fluorescent dye show a general dependence upon particle size, emission angle, and polarization conditions. However, for the excitation and detection conditions used in flow cytometry, the relative fluorescent intensities measured for the four particle sizes are proportional to the dye content to +10% accuracy, independent of particle size. Accordingly, the central dogma of flow cytometry 'that fluorescence is proportional to cellular dye content' is valid to this accuracy for these solid, highly refractive polymer particles. Most mammalian cells are much less refractive, therefore, should conform more closely to the central dogma.

Renal response to a saline load in well-compensated alcoholic cirrhosis

A total of 29 patients with well-compensated alcoholic cirrhosis and 9 healthy control subjects of similar age and sex were studied to assess their response to a challenge of 2 L of normal saline infused over a 1 hr period. Patients with cirrhosis had an adequate effective arterial blood volume in the basal state as assessed by neurohumoral markers of vascular filling. They also had a lower renal vascular resistance (p = 0.048) and a higher glomerular filtration rate (p = 0.014) than the controls, indicating the presence of renal vasodilation. Both groups were in sodium balance, but the patients with cirrhosis had a higher filtered load of sodium, an increased proximal tubular reabsorption of sodium (p = 0.015) and a decreased fractional excretion of sodium (p < 0.001). The administration of a saline load was not accompanied by any significant changes in the renal circulation in the patients with cirrhosis. They were unable to suppress their proximal tubular reabsorption of sodium to the same extent as the controls (p = 0.012), so by the fourth hour a significant difference in the rate of urinary excretion of sodium was evident. In the patients with cirrhosis, glomerular filtration rate before and after the saline load correlated significantly with indocyanine green extraction (r = 0.65; p = 0.002), whereas the tubular handling of sodium was dependent on antipyrine clearance (r = 0.80; p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental lead exposure inhibits adult rat retinal, but not kidney, Na+,K(+)-ATPase

Neonatal lead exposure produces selective rod degeneration and functional deficits in adult hooded rats. Similar alterations occur following retinal exposure to ouabain. This study determined whether there were long-term effects of neonatal lead exposure on rat retinal or renal Na+,K(+)-ATPase (Na,K-ATPase) activity and employed in vitro studies to examine the mechanism of ionic lead (Pb2+)-induced inhibition of retinal Na,K-ATPase. Pups, exposed to lead only via the milk of dams consuming 0, 0.02, or 0.2% lead solutions, had mean blood lead concentrations of 1.2, 18.8, and 59.4 micrograms/dl at weaning, respectively, and 5-7 micrograms/dl as adults. Prior lead exposure produced significant dose-dependent decreases in isolated retinal Na,K-ATPase activity (-11%; -26%) whereas activity in the kidney was unchanged. In contrast, Na,K-ATPase from both isolated control tissues was inhibited by Pb2+. The half-maximal inhibitory dose (I50) of Pb2+ for retinal and renal Na,K-ATPase was 5.21 x 10(-7) and 1.25 x 10(-5) M, respectively. The Hill coefficient of the retina was 0.42 whereas it was 0.88 in the kidney. With MgATP as a substrate, the Pb(2+)-induced inhibition of retinal Na,K-ATPase was competitive and reversible with a Ki of 2.1 x 10(-7) M. Retinal and renal Na,K-ATPase were 20-fold and 1.1-fold more sensitive to inhibition by Pb2+ than by Ca2+, respectively. The Pb(2+)-induced inhibition of retinal Na,K-ATPase was antagonized by Na+, potentiated by Mg2+, not altered by K+ or Ca2+, and prevented by ATP. Kinetic and competition studies with the retinal Na,K-ATPase establish that the Pb(2+)-induced inhibition is complex. The increased sensitivity of retinal, compared to renal, Na,K-ATPase to inhibition following in vivo or in vitro lead exposure may relate to their different alpha subunit composition. This is speculated to play a fundamental role in the target organ toxicity of lead.

Age dependence of cerebrovascular response mechanisms in domestic pigs

Hypercapnia-induced cerebral vasodilation in the newborn pig is a prostanoid-associated response. In some adult models, hypercapnic cerebral vasodilation is associated with the generation of nitric oxide (NO). Acetylcholine (ACh) produces a NO-dependent cerebral vasodilation in many adult models, but topical ACh is a prostanoid-associated cerebral vasoconstrictor in the newborn pig. We hypothesized that mediators influencing cerebral response can be age dependent. Juvenile domestic pigs were compared with newborn pigs, and pial arteriolar diameters were measured by use of a closed cranial window during hypercapnia and topical ACh (10(-5) M). Four different conditions were explored: control, topical N omega-nitro-L-arginine (L-NNA, 10(-3) M), indomethacin (5 mg/kg i.v.), and both L-NNA and indomethacin. All animals were anesthetized with alpha-chloralose. As opposed to the complete block in the newborn, indomethacin only partially attenuated the hypercapnic cerebral vasodilation in the juvenile pig.L-NNA, which had no effect on the response of the newborn, produced a partial attenuation of the hypercapnic response of the juvenile. The combination of indomethacin and L-NNA blocked the response in both age groups. Topical ACh in both age groups initially produced cerebral vasoconstriction, but, in the juvenile, this was followed by a sustained cerebral vasodilation. Indomethacin blocked the early vasoconstriction in both age groups. L-NNA, which had no effect in the response of the newborn to ACh, blocked the vasodilation seen in the juvenile. The combination of both inhibitors blocked all response to ACh in the juvenile. These data indicate that although the cerebral vascular responses to ACh and hypercapnia are prostanoid associated and NO independent in the newborn pig, NO assumes an increasing role in dilatory responses with development.

pHi in piglet cerebral microvascular endothelial cells: recovery from an acid load

Cerebral microvascular endothelial cells form a barrier between the blood and brain, which is critical for normal neuronal functions. These endothelial cells can be challenged by metabolic and respiratory acidosis, especially in newborn babies. We investigated mechanism(s) by which cerebral endothelial cells recover intracellular pH (pHi) when challenged with an intracellular acid load. pHi in piglet cerebral microvascular endothelial cells in primary culture was monitored using the pH-sensitive fluorescent dye BCECF (2',7'-bis-2-carboxyethyl-5(6)-carboxy-fluorescein acetoxymethyl ester), with dual wavelength fluorescence spectroscopy. Endothelial cells attached to coverslips and continuously superfused with HCO3-/CO2 containing medium (25 mM HCO3-, 5% CO2; pH 7.40) have a steady state of pHi of 7.18 +/- 0.02. Under basal conditions, amiloride (100 microMol) and H2DIDS (0.5 mM) decreased pHi 0.12 +/- 0.01 and 0.05 +/- 0.01 pH units, respectively. Removal of external Na+ lowered pHi 0.18 +/- 0.02pH units, while Cl- free medium decreased pHi 0.16 +/- 0.03pH units. These data suggest the presence of an amiloride-sensitive Na+-H+ exchanger and a Na+-dependent HCO3- -Cl- anion exchanger in endothelial cells. Propionate and high PCO2 cause rapid intracellular acidification at constant pH. The cells recover to control pHi over 10 min. Recovery from propionate was largely inhibited by amiloride, slightly inhibited by H2DIDS, and completely prevented by the combination. pHi recovery during elevated PCO2 was blocked by amiloride, H2DIDS, or Na+-free media. These results indicate that recovery from intracellular acidosis can involve amiloride-sensitive Na+-H+ exchange and a Na+-dependent HCO3-/Cl- anion exchange. Relative contributions of pumps and their independence appears to depend on the nature of the acid load.

Chief residency in PM&R. A balance of education and administration

The role of the Physical Medicine and Rehabilitation (PM&R) chief resident (CR) in physiatry residency education programs is the subject of annual deliberation in many academic centers. A national survey of PM&R programs was conducted to determine CR number, selection method, responsibilities, duration of service, and postresidency destiny. The questionnaire generated a response rate of 86% with 90% of programs reporting 1-3 CRs per year. A range of 1-11 CRs were selected annually per program. The most common methods of CR selection were faculty vote (45%), combined resident-faculty vote (22%), and other (33%). The prevalence of administrative responsibilities included orienting new residents (97%), formulating call schedules (92%), dispute mediation (88%), medical student-residency interviews (87%), rotation schedule configuration (64%), faculty meeting participation (61 %), social event promotion (59%), and elective and externship schedule development (31 %). Educational duties included teaching and organizing didactics (87%), organizing pharmaceutical and rehabilitation equipment inservices (77%), arranging didactics (77%), board review coordination (72%), arranging grand round speakers (66%), core curriculum lectures (61%), and facilitating resident research (37%). CR career goals included group practice (48%), academic faculty (29%), solo practice (5%), and fellowship (18%). Overall, PM&R CRs maintain considerable involvement in the educational aspects of residency training, although their clinical and administrative duties predominate. Although the PM&R CRs contribute significantly to the academic growth and development of their respective training programs, only a modest percentage (47%) of CRs choose to remain in academic physiatry via an attending (29%) or fellowship (18%) position.

A computer-aided design mammography screening system for detection and classification of microcalcifications

This paper presents a prototype of a computer-aided design (CAD) diagnostic system for mammography screening to automatically detect and classify microcalcifications (MCCs) in mammograms. It comprises four modules. The first module, called the Mammogram Preprocessing Module, inputs and digitizes mammograms into 8-bit images of size 2048x2048, extracts the breast region from the background, enhances the extracted breast and stores the processed mammograms in a data base. Since only clustered MCCs are of interest in providing a sign of breast cancer, the second module, called the MCCs Finder Module, finds and locates suspicious areas of clustered MCCs, called regions of interest (ROIs). The third module, called the MCCs Detection Module, is a real time computer automated MCCs detection system that takes as inputs the ROIs provided by the MCCs Finder Module. It uses two different window sizes to automatically extract the microcalcifications from the ROIs. It begins with a large window of size 64x64 to quickly screen mammograms to find large calcified areas, this is followed by a smaller window of size 8x8 to extract tiny, isolated microcalcifications. Finally, the fourth module, called the MCCs Classification Module, classifies the detected clustered microcalcifications into five categories according to BI-RADS (Breast Imaging Reporting and Data System) format recommended by the American College of Radiology. One advantage of the designed system is that each module is a separate component that can be individually upgraded to improve the whole system. Despite that it is still is a prototype system a preliminary clinical evaluation at TaiChung Veterans General Hospital (TCVGH) has shown that the system is very flexible and can be integrated with the existing Picture Archiving and Communications System (PACS) currently implemented in the Department of Radiology at TCVGH.

Dose-dependent effects of oral misoprostol on renal function in alcoholic cirrhosis

BACKGROUND/AIMS

Prostaglandins are important modulators of renal physiology, particularly when the effective circulatory volume is decreased. The aim of this study was to determine the dose-dependent effects of an oral prostaglandin E1 analogue, misoprostol, on renal function in patients with well-compensated alcoholic cirrhosis.

METHODS

Renal hemodynamics and tubular function were assessed by clearance techniques, before and after 100-microgram, 200-microgram, 400-microgram, or 800-microgram oral doses of misoprostol.

RESULTS

Overall, the results indicate that low-dose misoprostol is vasodilatory, natriuretic, and diuretic whereas high-dose misoprostol increases renal vascular tone and inhibits sodium and water excretion. The 200-microgram dose produced a transient but significant increase in the glomerular filtration rate and effective renal plasma flow and a decrease in renal vascular resistance. Urinary volume and urinary sodium excretion increased and urinary osmolality decreased.

CONCLUSIONS

The results suggest that, in patients with well-compensated cirrhosis, the renal effects of misoprostol are determined by a bell-shaped dose-response curve. The renal vasodilatory, natriuretic, and diuretic potential of 200-micrograms of misoprostol suggests that it may be of therapeutic value in patients with cirrhosis.

Genotypic analysis of primary head and neck squamous carcinoma by combined fluorescence in situ hybridization and DNA flow cytometry

Concurrent DNA flow cytometric (FCM) and fluorescence in situ hybridization (FISH) analyses were prospectively performed on 24 primary untreated head and neck squamous carcinomas for characterization of the genotypic and phenotypic DNA aberrations of these neoplasms. Eleven tumors (42.0%) manifested DNA diploidy (DI = 1.00) and 15 (58.0%) had DNA aneuploidy (DI < or > 1.00) by FCM. Fluorescence in situ hybridization results showed aneusomy in the majority of DNA diploid and in all DNA aneuploid tumors. The extent of the abnormalities for individual chromosomes and the number of involved chromosomes in a given DNA diploid or aneuploid tumor were significantly different. Overall, a statistical correlation between the FCM DNA index (DI) and the magnitude of the chromosomal aberration by FISH was found. Our results also show a significant association between the DI and histologic differentiation and stage of disease in these neoplasms. In conclusion, (1) chromosomal aneusomy characterizes most DNA diploid (DI = 1.00) and all DNA aneuploid (DI < or > 1.00) head and neck squamous carcinomas; (2) polysomy is the most prevalent finding; (3) loss of the Y chromosome in tumors from male patients is a consistent feature; (4) the FCM DI reflects net chromosomal gains or losses in these neoplasms; and (5) DNA aneuploidy is associated with tumor aggressiveness.

Prostanoid synthesis in response to high CO2 in newborn pig brain microvascular endothelial cells

Hypercapnia-induced cerebral vasodilation involves prostanoids in newborn pigs. However, the source of prostanoids has not been determined. The current study was designed to address the hypothesis that piglet cerebral microvascular endothelial cells increase their synthesis of prostanoids in response to high CO2. Microvascular endothelial cells, smooth muscle cells, and glia were isolated and grown in primary culture. They were identified morphologically and by indirect immunofluorescence staining. Cerebral microvascular endothelial cell cultures from newborn pigs produced equal amounts of 6-ketoprostaglandin (PG) F1 alpha (stable hydrolysis product of PGI2), PGE2 and a small amount of PGF2 alpha under basal conditions. Administration of calcium ionophore A23187 to the endothelial cells increased release of all three prostanoids in a dose- and time-dependent manner. Exposure of piglet cerebral microvascular endothelial cells to higher than normal CO2 increased the production of 6-keto-PGF1 alpha and PGE2 but not of PGF2 alpha. The enhanced prostanoid biosynthesis was concentration dependent, peaking at 14% CO2, and was detected during the first 10 min exposure to 14% CO2. Hypercapnia-induced increased synthesis of prostanoids was blocked dose dependently by the simultaneous addition of PGH synthase inhibitor indomethacin. High CO2 did not increase prostanoid production by cerebral microvascular smooth muscle cells or glia, although A23187 enhanced prostanoid formation by both cell types. These data show that high CO2 stimulates prostanoid synthesis by newborn pig cerebral microvascular endothelial cells, which is consistent with an involvement of cerebral vascular endothelium in hypercapnia-induced vasodilation.

Isocitrate dehydrogenase from bovine heart: primary structure of subunit 3/4

Bovine NAD(+)-dependent isocitrate dehydrogenase was shown previously to contain four subunits of approx. 40 kDa (subunits 1-4) possessing different peptide maps and electrophoretic properties [Rushbrook and Harvey (1978) Biochemistry 17, 5339-5346]. In this study the heterogeneity is confirmed using enzyme purified by updated methods and from single animals, ruling out allelic variability. Subunits 1 and 2 were differentiated from each other and from subunits 3 and 4 by N-terminal amino acid sequencing. Subunits 3 and 4 (subunits 3/4) were identical in sequence over 30 residues. The N-terminal residues of subunits 1 and 2 were homologous but not identical with the beta- and gamma-subunits respectively of the comparable pig heart enzyme. Subunits 3/4 were identical over 30 residues with the N-terminus of the pig heart alpha-subunit. Full-length sequence, including that for mitochondrial import, is presented for a protein with the processed N-terminus of subunits 3/4, deduced from cloned cDNA obtained utilizing the N-terminal sequence information. The derived amino acid sequence for the mature protein contains 339 amino acids and has a molecular mass of 36,685 Da. Complete identity with N-terminal and Cys-containing peptides totalling 92 residues from the alpha-subunit of the pig heart enzyme [Huang and Colman (1990) Biochemistry 29, 8266-8273] suggests that maintenance of a particular three-dimensional structure in this subunit is crucial to the function of the enzyme. An electrophoretic heterogeneity within the pig heart alpha-subunit, similar to that shown by bovine subunits 3/4, was demonstrated. One reordering of the Cys-containing peptides of the pig heart alpha-subunit is indicated. Sequence comparison with the distantly related NADP(+)-dependent enzyme from Escherichia coli, for which the three-dimensional structure is known [Stoddard, Dean and Koshland (1993) Biochemistry 32, 9310-9316] shows strong conservation of residues binding isocitrate, Mg2+ and the NAD+ moiety of NADP+, consistent with a catalytic function.