Exploring the basis of peptide-carbohydrate crossreactivity: evidence for discrimination by peptides between closely related anti-carbohydrate antibodies

To investigate the molecular basis of antigenic mimicry by peptides, we studied a panel of closely related mAbs directed against the cell-wall polysaccharide of group A Streptococcus. These antibodies have restricted V-gene usage, indicating a shared mechanism of binding to a single epitope. Epitope mapping studies using synthetic fragments of the cell-wall polysaccharide supported this conclusion. All of the mAbs isolated crossreactive peptides from a panel of phage-displayed libraries, and competition studies indicated that many of the peptides bind at or near the carbohydrate binding site. Surprisingly, the peptides isolated by each mAb fell into distinct consensus-sequence groups that discriminated between the mAbs, and in general, the peptides bound only to the mAbs used for their isolation. Similar results were obtained with polyclonal antibodies directed against synthetic oligosaccharide fragments of the streptococcal cell-wall polysaccharide. Thus, the peptides appear to be specific for their isolating antibodies and are not recognized by the same mechanism as their carbohydrate counterparts.

The differential and temporal effects of antecedent exercise on the self-stimulatory behavior of a child with autism

The effects of two levels of exercise (walking versus jogging) in suppressing the self-stimulatory behavior of a five-year-old boy with autism were examined. The exercise conditions were applied immediately before periods of academic programming. Maladaptive self-stimulatory behaviors were separately tracked, enabling identification of behaviors that were more susceptible to change (e.g., physical self-stimulation and "out of seat" behavior) versus those that were more resistant (e.g., visual self-stimulation). Examination of temporal effects indicated a decrease in physical self-stimulation and "out of seat" behavior, but only for the jogging condition. In addition, sharp reductions in these behaviors were observed immediately following the jogging intervention and gradually increased but did not return to baseline levels over a 40 min period. Implications for further research and clinical intervention are discussed.

Tuberculosis outbreak in a Texas prison, 1994

In 1994 a Texas prison containing a population of mentally retarded inmates experienced a large tuberculosis outbreak. Fifteen cases of tuberculosis were identified (8 confirmed by positive cultures for Mycobacterium tuberculosis) and more than 100 inmates became infected. The culture-confirmed patients were infected with an identical strain of tuberculosis as demonstrated by polymerase chain reaction (PCR) based DNA fingerprinting technique. The prison followed standard tuberculosis infection control policies, but these controls were inadequate to prevent tuberculosis transmission in this special population. Two hundred and thirty inmates (119 inmates showing evidence of new tuberculosis infection or active disease and 111 healthy controls) were enrolled in the investigation. Inmate cell assignments, job duties, and educational classes were identified and medical chart reviews were conducted on all inmates. Tuberculosis transmission was associated with residing on the D Wing of the prison (OR = 25.84, P < 0.01), attending school in Classroom A (OR = 8.34, P = 0.01) and working on the prison utility work crew (OR = 2.52, P < 0.01). The index case in the outbreak had been prescribed 6 months of isoniazid (INH) chemoprophylaxis in 1988.

Localization of a yeast early Golgi mannosyltransferase, Och1p, involves retrograde transport

To analyze the mechanism of integral membrane protein localization in the early Golgi apparatus of Saccharomyces cerevisiae, we have used Och1p, a cis-Golgi mannosyltransferase. A series of influenza virus hemagglutinin (HA) epitope-tagged fusion proteins was constructed in which invertase is appended to the Golgi-luminal carboxy terminus of full-length Och1p. Several constructs included a Kex2p cleavage site between the Och1p and invertase moieties to monitor transit to the Kex2p-containing TGN. Cells expressing an Och1p-invertase fusion do not secrete invertase, but those expressing an Och1p-Kex2p site-invertase fusion protein secrete high levels of invertase in a Kex2p-dependent manner. The Och1p-Kex2p site-invertase fusion protein is cleaved with a half-time of 5 min, and the process proceeds to completion. Before cleavage the protein receives glycosyl modifications indicative of passage through the medial- and trans-Golgi, therefore cleavage occurs after ordered anterograde transport through the Golgi to the TGN. Transit to distal compartments is not induced by the invertase moiety, since noninvertase fusion constructs encounter the same glycosyltransferases and Kex2p as well. The Och1p-HA moiety, irrespective of whether it is generated by cleavage of the fusion protein in the TGN or synthesized de novo, is degraded with a half-time of about 60 min. Thus, the half-time of degradation is 12-fold longer than the time required to reach the TGN. At steady state, de novo-synthesized and TGN-generated HA epitope-tagged Och1p reside in a compartment with a buoyant density identical to that of wild-type Och1p and distinct from that of the vacuole or the TGN. Finally, och1 null cells that express an Ochlp fusion construct known to rapidly encounter the TGN glycosylate invertase to the same extent as wild-type cells, indicating that they have phenotypically wild-type Och1p activity. These results lead us to propose a model for Och1p-HA localization that involves movement to distal compartments, at least as far as the TGN, followed by retrieval to the cis compartment, presumably by vesicular transport.

Transferred nuclear Overhauser enhancement experiments show that the monoclonal antibody strep 9 selects a local minimum conformation of a Streptococcus group A trisaccharide-hapten

Transferred nuclear Overhauser enhancement (TRNOE) experiments have been performed to investigate the bound conformation of the trisaccharide repeating unit of the Streptococcus Group A cell-wall polysaccharide. Thus, the conformations of propyl 3-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-2-O-(alpha-L-rhamnopyran osyl)- alpha-L-rhamnopyranoside [C(A')B] (1) as a free ligand and when complexed to the monoclonal antibody Strep 9 were examined. Improved insights about the conformational preferences of the glycosidic linkages of the trisaccharide ligand showed that the free ligand populates various conformations in aqueous solution, thus displaying relatively flexible behavior. The NOE HNAc-H2A', which was not detected in previous work, accounts for a conformation at the beta-(1-->3) linkage with a phi angle of approximately 180 degrees. Observed TRNOEs for the complex are weak, and their analysis was further complicated by spin diffusion. With the use of transferred rotating-frame Overhauser enhancement (TRROE) experiments, the amount of spin diffusion was assessed experimentally, proving that all of the observed long-range TRNOEs arose through spin diffusion. Four interglycosidic distances, derived from the remaining TRNOEs and TRROEs, together with repulsive constraints, derived from the absence of TRROE effects, were used as input parameters in simulated annealing and molecular mechanics calculations to determine the bound conformation of the trisaccharide. Complexation by the antibody results in the selection of one defined conformation of the carbohydrate hapten. This bound conformation, which is a local energy minimum on the energy maps calculated for the trisaccharide ligand, shows only a change from a +gauche to a -gauche orientation at the psi angle of the alpha-(1-->2) linkage when compared to the global minimum conformation. The results infer that the bound conformation of the Streptococcus Group A cell-wall polysaccharide is different from its previously proposed solution structure (Kreis et al., 1995).

The effect of articular conformity and the size of the humeral head component on laxity and motion after glenohumeral arthroplasty. A study in cadavera

We used a cadaveric model to examine the mechanical effects of changes in the conformity of the articular surfaces and the size of the humeral head component in glenohumeral arthroplasty. The experimental system permitted a manual clinical examination of the glenohumeral joint while sensors monitored the humeroscapular position and orientation as well as the forces and torques applied by the examiner. Four preparations were compared: an anatomical humeroscapular preparation and three glenohumeral arthroplasty preparations (one with anatomically sized components and a radius of curvature of the glenoid that was four millimeters larger than that of the humeral head, one with anatomically sized components and a radius of curvature of the glenoid that was equal to that of the humeral head, and one with a non-anatomical, large humeral head component and a radius of curvature of the glenoid that was equal to that of the humeral head). All motions, including flexion, external and internal rotation, and maximum elevation, were diminished with use of the non-anatomical, large humeral head component. Laxity of the joint on drawer and sulcus tests was not affected by the conformity of the articular surfaces but was decreased significantly by implantation of the large humeral head component. The kinematics of the glenohumeral joint were not markedly altered by reduction of the uniformity between the articular surfaces of the prosthetic components. In all preparations, obligate displacement of the humeral head associated with a passive range of motion occurred at smaller angles with the large humeral head component.

Teaching children with autism to seek information: acquisition of novel information and generalization of responding

A time delay procedure was used to teach 3 children with autism to ask the question "What's that?" when novel stimuli were presented during an instructional task. Once the ability to ask the question was acquired, the children's ability to learn novel information by asking the question was assessed. The children were then taught to ask the question within a less structured context. All three studies used a multiple baseline across participants. Generalization was assessed in a different room, to a new person, and to novel stimuli. All of the children learned to ask the question within the instructional context, while on a walk in the school building, and to request information about three-dimensional objects. The acquisition of novel information was consistent for receptive and expressive tests for 2 of the children, with varied results for the 3rd. These studies indicate that children with autism can be taught to ask questions that lead to the acquisition of new information.

Dominant lethal mutations in the plasma membrane H(+)-ATPase gene of Saccharomyces cerevisiae

The plasma membrane H(+)-ATPase of Saccharomyces cerevisiae is an essential protein that is required to establish cellular membrane potential and maintain a normal internal pH. An Asp-378 to Asn substitution at the residue phosphorylated during catalysis is dominant lethal when the pma1-D378N mutation is expressed along with a wild-type plasma membrane H(+)-ATPase (PMA1) gene. Several mutations in the first two putative transmembrane domains are also dominant lethal. However, these dominant lethal mutants often appear to be innocuous, because they are frequently lost by gene conversion to the wild-type sequence during the process of introducing the mutant sequence and subsequently removing the wild-type gene. Loss of the mutation by gene conversion does not occur while introducing recessive lethal mutations. Cells carrying the wild-type PMA1 gene on the chromosome and a dominant lethal mutation under the control of a GAL1 promoter on a centromere-containing plasmid exhibit a galactose-dependent lethality. Indirect immunofluorescence staining using anti-Pma1 antibodies shows that induction of dominant lethal PMA1 mutations leads to the accumulation of a number of intensely staining cytoplasmic structures that are not coincident with the nucleus and its immediately surrounding endoplasmic reticulum. These structures also accumulate the endoplasmic reticulum protein Kar2. Expression of the dominant lethal protein also prevents transport of the wild-type ATPase to the plasma membrane.

In vivo quantification of the laxity of normal and unstable glenohumeral joints

The purpose of this study was to determine whether the magnitude of glenohumeral translation on clinical laxity tests could distinguish between clinically stable shoulders and shoulders with traumatic or atraumatic instability. Subjects included eight male volunteers with no history of symptoms of glenohumeral instability, eight patients with documented traumatic anterior instability and Bankart lesions, and eight patients with documented atraumatic multidirectional instability. The patients in the two instability groups had disabling instability that was refractory to nonoperative management and thus met the indications for surgical repair. All subjects were examined by an experienced shoulder surgeon using five standard manual tests: anterior drawer, posterior drawer, sulcus, push-pull, and fulcrum. The glenohumeral translations occurring during these laxity tests were quantitated with a spatial sensing system that had six degrees of freedom and was rigidly fixed to the scapula and humerus. The result showed substantial overlap in the translations found in members of the three groups for each of the laxity tests. Standard laxity tests demonstrate considerable translation in normal glenohumeral joints and do not reliably differentiate normal shoulders from those with two common forms of glenohumeral instability. This study suggests that assessment of the magnitude of glenohumeral translation on clinical laxity tests is not a specific test for the diagnosis of glenohumeral instability. Healthy subjects without symptoms may have as much translation as patients needing surgical repair for symptomatic shoulder instability. The need for and the type of surgical reconstruction for the unstable shoulder must be based on the patient's history and on duplication of the symptoms of instability on directed physical examination rather than on the magnitude of glenohumeral translation.

Community-based behavioral training approaches for people with mental retardation and mental illness

Challenges associated with behavioral training approaches for individuals with mental retardation and mental illness in the community are reviewed in this article. Family and nonfamily facilitated training are considered. Professional practice issues are reviewed, and justification for multifactor behavioral assessment is offered. Future research directions are discussed.

Arthroscopic labral repair to the glenoid rim

The purpose of this study was to develop a new arthroscopic approach for traumatic instability that effectively reattaches avulsed capsulolabral tissue to the glenoid articular rim with sutures. This technique does not depend on fixation devices, trans-scapular drilling, or implantation of suture anchors. We attached a three-dimensional position sensor and force and torque transducer to the humerus and scapula of eight normal cadaveric shoulders to measure the normal, surgically unstable (arthroscopic Bankart lesion), and repaired preparations. We assessed eight motion ranges and six laxity tests. Capsulolabral release increased all passive ranges and allowed significant translational increases on posterior drawer and crank testing. After repair, motion was never decreased and there were no differences in laxity relative to normal. Neurovascular structures were never at risk. Our arthroscopic repair provides anatomic reattachment and effective deepening of the glenoid con-cavity similar to that achieved by open repair. This new method restores joint stability, preserves motion, and can withstand forceful loads. Ongoing clinical trials will substantiate whether the technique is as safe and reliable as shown cadaverically.

Residual motion and function after glenohumeral or scapulothoracic arthrodesis

The purpose of this study was to characterize humerothoracic motion and function after glenohumeral or scapulothoracic arthrodesis and to compare those results with those from normal shoulders. We evaluated 12 shoulders in 11 patients at an average of 71 months after glenohumeral arthrodesis and seven shoulders in six patients at an average of 32 months after scapulothoracic arthrodesis. The residual motion of the unfused articulation was measured with a spatial position sensor. Various activities of daily living and standard clinical range-of-motion tests were performed. Nearly all humerothoracic motions were significantly decreased in patients after either type of shoulder arthrodesis. Patients with a glenohumeral fusion maintained their scapulothoracic motion at levels comparable with that of normal subjects. Residual glenohumeral extension and external rotation after scapulothoracic fusion were significantly decreased; internal rotation remained unchanged compared with motion in subjects with normal shoulders. Glenohumeral fusion decreased the patients' ability to perform personal care activities requiring extremes of internal rotation or elevation. Although glenohumeral arthrodesis limited total humerothoracic motion considerably, the majority of patients were improved functionally and were relatively free from pain. Most personal care activities were performed successfully by all patients with scapulothoracic fusion.

Inadvertent administration of rtPA to a patient with type 1 aortic dissection and subsequent cardiac tamponade

Administration of thrombolytic agents to patients with misdiagnosis of acute myocardial infarction can result in serious side effects. A case of aortic dissection that was misdiagnosed as acute myocardial infarction and received rtPA is reported. Within 1 hour of rtPA infusion, the patient developed cardiac tamponade. Type 1 aortic dissection was diagnosed by aortic angiogram. The patient underwent emergency resection of the dissection and evacuation of the pericardial and anterior mediastinal hematoma. Although he required massive transfusion of blood products intraoperatively, he is doing well 22 months after his surgery.

Convergent synthesis of an elusive hexasaccharide corresponding to the cell-wall polysaccharide of the beta-hemolytic Streptococcus group A

A convergent synthesis of a hexasaccharide corresponding to the cell-wall polysaccharide of the beta-hemolytic Streptococcus Group A is described. The strategy relies on the preparation of a key linear trisaccharide unit beta-D-GlcpNAc-(1-->3)-alpha-L-Rhap-(1-->2)-alpha-L-Rhap which has previously resisted our efforts. The trisaccharide functions both as a glycosyl acceptor and donor to give an elusive hexasaccharide. This fully functionalized unit can serve, in turn, as a glycosyl acceptor or donor for the synthesis of higher-order structures. Deprotection gives a hitherto unknown hexasaccharide for use as a hapten in immunochemical studies. The characterization of all compounds by high-resolution 1H and 13C NMR spectroscopy is also described.

Resolution of infantile Erb's palsy utilizing chiropractic treatment

OBJECTIVE

To present a case study of infantile Erb's palsy that responded to conservative chiropractic care.

CLINICAL FEATURES

A 5-wk-old infant boy suffered from a limp left arm. A clinical diagnosis of Erb-Duchenne palsy was made. Birth records were obtained to further substantiate the diagnosis.

INTERVENTION AND OUTCOME

The patient received specific chiropractic adjustments to the mid-cervical spine and muscle stimulation therapy with an upper extremity exercise program. The Erb's palsy resolved with only a mild residual "waiters tip" deformity within 2 months.

CONCLUSION

In this case, chiropractic adjustments with muscle stimulation therapy is suggested as an effective treatment for Erb's palsy. Further studies are required to better understand chiropractic's effectiveness in Erb's palsy cases.

Enhanced cytochrome-oxidase staining of the cuneate nucleus in the rat reveals a modifiable somatotopic map

Existing cytochrome oxidase (CO)-staining techniques were modified to enhance sensitivity and contrast in order to examine patterns of CO-activity in the dorsal column nuclei (DCN) of adult Long-Evans rats. Within a rostrocaudally limited region in the middle of the cuneate nucleus (CN) distinctive blotches of intense CO-activity were observed. The CO-staining was maximally differentiated approximately 0.3-0.7 mm caudal to the obex. No CO-blotches were observed anywhere else in the DCN. Transganglionic labelling (WGA-HRP) demonstrated that some of the CO-blotches in the rat CN are related to the terminal projection fields of primary afferents from the skin of the forepaws. The corresponding location of primary afferent termination fields and CO-staining patterns supports a tripartite rostrocaudal division in the rat CN, similar to that described by other investigators in cats, monkeys and raccoons. Comparing the patterns of CO-staining to (1) the cytoarchitecture (Nissl-stained sections), or to (2) the dendritoarchitecture (distribution of microtubule-associated protein 2 (MAP2) or to (3) the organization of retrogradely labelled (WGA-HRP/HRP) cuneothalamic cells, revealed no topographical organization corresponding to the CO-blotches. Postnatal (at least up to 11 days postpartum) forepaw deafferentation or removal disrupted the CO-staining pattern in the CN.

Rapid, synchronous, and stable induction of type 1 piliation in Escherichia coli by using a chromosomal lacUV5 promoter

Type 1 pili are filamentous proteinaceous appendages produced by certain members of the family Enterobacteriaceae. In Escherichia coli, the adhesive properties of these pili are due to the binding of at least one minor pilus component to mannose, a sugar common to cell surface molecules of many eukaryotic cells. The study of pilus assembly may be benefited by a rapid way of inducing pilus synthesis de novo. We describe herein the construction and characterization of a strain in which piliation can be rapidly induced by the addition of lactose or its analog isopropyl-beta-D-thiogalactopyranoside. This was accomplished by placing the chromosomal fimA gene (encoding the major structural subunit of pili) under lacUV5 promoter control. Further experiments suggested that transcription of genes downstream of fimA, whose products are required for normal pilus assembly and function, may also be controlled by the lacUV5 promoter. The construction described herein may have a variety of applications apart from aiding the study of pilus assembly since its adhesive properties can be rapidly and easily turned on and off.

Glenohumeral stability from concavity-compression: A quantitative analysis

The purpose of this research was to determine the degree to which compression of the humeral head into the glenoid concavity stabilizes it against translating forces. Ten normal fresh-frozen cadaver glenohumeral joints in which the labrum was preserved were used. A compressive load of 50 N was applied to the humeral head in a direction perpendicular to the glenoid surface. Increasing tangential forces were then applied until the head dislocated over the glenoid lip. The tangential force at dislocation was examined for eight different directions, 45° apart around the glenoid. Concavity-compression stability was then examined for an increased compressive load of 100 N. Finally, the protocol with 50 and 100 N of compressive load was repeated after the glenoid labrum was excised. Concavity-compression of the humeral head into the glenoid is a most efficient stabilizing mechanism. With the labrum intact the humeral head resisted tangential forces of up to 60% of the compressive load. The degree of compression stabilization varied around the circumference of the glenoid with the greatest magnitude superiorly and inferiorly. This may be attributed to the greater glenoid depth in these directions. Resection of the glenoid labrum reduced the effectiveness of compression stabilization by approximately 20%. These results indicate that concavity-compression may be an important mechanism for providing stability in the mid-range of glenohumeral motion where the capsule and ligaments are lax. The effectiveness is enhanced by the presence of an intact glenoid labrum.

Convergent synthesis of higher-order oligosaccharides corresponding to the cell-wall polysaccharide of the beta-hemolytic Streptococci group A. A branched hexasaccharide hapten

A convergent synthesis of a hexasaccharide corresponding to the cell-wall polysaccharide of the beta-hemolytic Streptococci Group A is described. The strategy relies on the preparation of a key branched trisaccharide unit alpha-L-Rhap-(1----2)-[beta-D-GlcpNAc-(1----3)]-alpha-L-Rhap which functions both as a glycosyl acceptor and donor. The hexasaccharide is obtained after only three glycosylation reactions. This fully functionalized unit can serve, in turn, as a glycosyl acceptor or donor for the synthesis of higher-order structures. Deprotection gives a hexasaccharide for use as a hapten in immunochemical studies. The characterization of all compounds by high resolution 1H- and 13C-n.m.r. spectroscopy is also described.

The role of the rotator interval capsule in passive motion and stability of the shoulder

The purpose of this study was to characterize the role of the capsule in the interval between the supraspinatus and subscapularis tendons with respect to glenohumeral motion, translation, and stability. We used a six-degrees-of-freedom position-sensor and a six-degrees-of-freedom force and torque-transducer to determine the glenohumoral rotations and translations that resulted from applied loads in eight cadaver shoulders. The range of motion of each specimen was measured with the capsule in the rotator interval in a normal state, after the capsule had been sectioned, and after it had been imbricated. Operative alteration of this capsular interval was found to affect flexion, extension, external rotation, and adduction of the humerus with respect to the scapula. Modification of this portion of the capsule also affected obligate anterior translation of the humeral head on the glenoid during flexion. Limitation of motion and obligate translation were increased by operative imbrication and diminished by sectioning of the rotator interval capsule. Passive stability of the glenohumeral joint was evaluated with the use of anterior, posterior, and inferior stress tests. Instability and occasional frank dislocation of the glenohumeral joint occurred inferiorly and posteriorly after section of the rotator interval capsule. Imbrication of this part of the capsule increased the resistance to inferior and posterior translation.

Laxity of the normal glenohumeral joint: A quantitative in vivo assessment

It is critical that surgeons comprehend the normal laxity of the glenohumeral joint (1) to assist them in diagnosing conditions of clinical instability and (2) to help define a therapeutic end point for the management of shoulders with excessive stiffness. In clinical practice this joint laxity is judged by standard manual tests. We report a quantitative study of the clinical in vivo laxity of the normal shoulders of eight male volunteers. To our knowledge this is the first time that the laxity revealed on standard manual clinical tests has been quantified in vivo. The relative motions of the humerus and scapula were determined with an electromagnetic spatial tracker. This device was pinned percutaneously to the humerus and scapula of each of eight normal male volunteers of ages 25 to 45 years. An experienced shoulder surgeon carried out standard manual clinical tests of glenohumeral laxity while the resulting displacements of the humeral head relative to the glenoid were measured. Spatial tracker data indicated that for each of the different tests, the positions of the glenohumeral and scapulothoracic joints were reproducible for a given subject and among subjects. Substantial glenohumeral translations were measured during those manual laxity tests in which the joint was not at the limit of its range of motion: the drawer test, 7.8 ± 4.0 mm anterior and 7.9 ± 5.6 mm posterior; the sulcus test, 10.6 ± 3.8 mm inferior; and the push-pull test, 9.0 ± 6.3 mm posterior. A minimal translation of 0.3 ± 2.5 mm was measured during the fulcrum test in which the glenohumeral ligaments were under tension. The observed translations were reproducible in each subject's shoulder. On the other hand, there was marked variability among subjects. Even though manual laxity tests are a standard part of the clinical evaluation of the shoulder, our finding that normal glenohumeral joints show substantial translations indicates that translation on clinical manual laxity testing is not in and of itself a sufficient indication for surgical stabilization.

A system for describing positions of the humerus relative to the thorax and its use in the presentation of several functionally important arm positions

The function of the shoulder is to position the arm with respect to the thorax. Humerothoracic positions are commonly described in terms of the degrees of humeral elevation in the sagittal plane (flexion) and/or the degrees of elevation in the coronal plane (abduction). This article proposes a more general system for describing positions of the arm based on the plane of humeral elevation and the angle of elevation within this plane. This system is used to present the humerothoracic positions used by eight normal subjects to perform several activities of daily living as well as those achieved in a range-of-motion examination of the shoulder. Eating, hair combing, and maximal elevation were all performed in a plane approximately 60° anterior to the coronal plane. Between reaching the perineum and washing the contralateral axilla, the humerus functioned in a range of planes extending over 180°.

Evidence for coupling between membrane and cytoplasmic domains of the yeast plasma membrane H(+)-ATPase. An analysis of intragenic revertants of pma1-105

A genetic approach was used to identify interacting portions of the plasma membrane H(+)-ATPase from Saccharomyces cerevisiae. The cellular sensitivity of the pma1-105 strain (S368F) to low external pH and to NH4+ was used to select intragenic revertants of two classes: phenotypically wild-type full revertants and partial revertants that were low pH-resistant but retained resistance to hygromycin B. All 10 full revertants had S368 restored. Among five partial revertants mapping to the original site within the phosphorylation domain, S368L and S368V were each found twice. One revertant contained an E367V substitution adjacent to the original S368F alteration. Four of 13 independently isolated second-site revertants mapped to one site, V289F, in the proposed phosphatase domain. Mutations within the proposed phosphatase and phosphorylation domains resulted in enzymes with increased vanadate sensitivity relative to the vanadate-insensitive S368F enzyme. These results suggest that sites S368, E367, and V289 contribute to a vanadate (Pi) binding domain or are able to interact with such a site within the catalytic domain. The remaining nine partial second-site revertants mapped to six sites within the putative transmembrane regions. Mutations within the transmembrane region had less of an effect on vanadate sensitivity. Most revertant enzymes showed small but significant increases in the rate of ATP hydrolysis relative to the S368F enzyme. Several enzymes no longer displayed the acid-sensitive pH-dependence seen in the S368F enzyme. These data provide novel evidence for an interaction between putative transmembrane helices 1-3 and 7 and the ATP hydrolytic portion of the enzyme.