Mitochondrial FAD-glycerophosphate dehydrogenase and G-protein-coupled inwardly rectifying K+ channel: No evidence for linkage in maturity-onset diabetes of the young or NIDDM

Two genes that have potentially important regulatory roles in insulin secretion are both located on chromosome 2q24.1. G-protein-coupled muscarinic potassium channel (GIRK1) is an inwardly rectifying K+ channel that helps to maintain the resting potential and excitability of cells. Mitochondrial FAD-linked glycerophosphate dehydrogenase (m-GDH) catalyzes a rate-limiting step of the glycerol phosphate shuttle in pancreatic islets. Reduced m-GDH activity has been demonstrated in islets isolated from diabetic subjects compared with islets from nondiabetic control subjects and from the diabetic GK rat. To study the relationship between these candidate genes and NIDDM, we have examined a simple tandem-repeat polymorphism (STRP) close to both the KCN J3 (GIRK1) locus and the m-GDH locus. In a linkage study of three maturity-onset diabetes of the young (MODY) pedigrees, not linked to MODY1, MODY2, or MODY3, a cumulative score of - 9.6 at a recombination fraction of theta = 0 excluded linkage. In a population-association study, no linkage disequilibrium for the STRP was found between 190 unselected NIDDM patients and 60 geographically and age-matched white nondiabetic subjects (chi2 = 1.51 on 3 df, P = 0.68). Thus, mutations involving the genes for GIRK1 or FAD-glycerophosphate dehydrogenase are unlikely to cause MODY, and a common mutation in either gene is unlikely to contribute to NIDDM in whites. These data do not exclude mutations in some families or other ethnic groups.

Development of a skin model based on insoluble fibrillar collagen

A biocompatible, 3-dimensional, noncontracting, crosslinked collagen matrix was adapted to promote differentiation of epidermal keratinocytes. To produce the matrix, a 3% wt/wt dispersion of insoluble bovine collagen containing 5 mg polylysine/g collagen in 0.001 N HCl was blended, lyophilized, and crosslinked using a dehydrothermal technique. Matrices 4 cm2 and 3 mm thick were seeded with human dermal fibroblasts (1 x 10(5)/cm2). After 5 days in culture, the matrices were seeded with human epidermal keratinocytes (1 x 10(5)/cm2). The cultures were grown submerged for 1 week and raised to the liquid/air interface for 3 weeks to promote epidermal differentiation. Based on morphology and immunological staining with antibodies for human involucrin, keratin 1 (k1), filaggrin, and loricrin, the state of differentiation of the epidermal layer was nearly equivalent to that seen with cultures grown on contracted collagen lattices produced according to the methodology described in the literature and similar to the pattern produced in normal neonatal foreskin. These results demonstrate the usefulness of an in vitro skin model employing a crosslinked collagen matrix that permits the incorporation of additional covalently linked bioactive molecules during matrix formation.

Dental caries and sealant usage in U.S. children, 1988-1991: selected findings from the Third National Health and Nutrition Examination Survey

This article provides estimates of dental caries and dental sealant use among U.S. children and adolescents, obtained from Phase 1 (1988-1991) of the Third National Health and Nutrition Examination Survey. More than 60 percent of children under the age of 10 years had a caries-free primary dentition; among children and adolescents aged 5 to 17 years, about 55 percent had a caries-free permanent dentition. The highest percentages of dental caries among children and adolescents continue to be distributed disproportionally among about 25 percent of the U.S. population. Fewer than one in five U.S. children and adolescents aged 5 to 17 years had one or more sealed permanent teeth.

Coronal and root caries in the dentition of adults in the United States, 1988-1991

Dental public health policy planning requires accurate and current information about the extent of caries in the United States population. These data are available from the caries examination from Phase 1 of the Third National Health and Nutrition Examination Survey, which found that 94% of adults in the United States show evidence of past or present coronal caries. Among the dentate, the mean number of decayed and filled coronal surfaces per person was 21.5. Dentate females had a lower number of untreated coronal tooth surfaces with caries (1.5), but a higher mean number of treated and untreated surfaces per person (22.7) than males, with scores of 2.1 and 20.2, respectively. Estimates for race-ethnicity groups were standarized by age and gender to control for population differences among them. Dentate non-Hispanic blacks (11.9) and Mexican-Americans (14.1) had half the number of decayed and filled coronal surfaces as non-Hispanic whites (24.3), but more untreated surfaces (non-Hispanic whites, 1.5; non-Hispanic blacks, 3.4; Mexican-Americans, 2.8). Mexican-Americans were most likely to be dentate, had the highest average number of teeth, and had 25% fewer decayed, missing, and filled coronal surfaces (37.6) than non-Hispanic blacks (49.2) and non-Hispanic whites (51.0). Root caries affected 22.5% of the dentate population. Blacks had the most treated and untreated root surfaces with caries (1.6), close to the value for Mexican-Americans (1.4). The score for non-Hispanic whites was 1.1. Untreated root caries is most common in dentate non-Hispanic blacks (1.5), followed by Mexican-Americans (1.2), with non-Hispanic whites (0.6) having the fewest untreated carious root surfaces. Race-ethnicity groups were disparate with respect to dental caries; effort is needed to treat active caries common in some population subgroups.

Coronal caries in the primary and permanent dentition of children and adolescents 1-17 years of age: United States, 1988-1991

The Third National Health and Nutrition Examination Survey-Phase 1, conducted from 1988 to 1991 in the United States, included an assessment of dental caries in US children and adolescents and provided the opportunity for differences in dental caries status to be viewed by a ge, sex, race, and race-ethnicity. The measurement of dental caries in children and adolescents from 2-17 years of age included the number of decayed, missing, and filled permanent tooth surfaces and teeth, and the number of decayed, and filled primary tooth surfaces and teeth. Additionally, a brief visual inspection for the presence or absence of early childhood caries in the maxillary incisors was conducted for children 12-23 months of age. The survey yielded weighted estimates for 1988-1991 for over 58 million US children and adolescents 1 to 17 years of age. For infants aged 12-23 months, 0.8% were scored positive for early childhood caries. Over 60% (62.1%) of the children aged 2-9 years were caries-free in their primary dentition. Over half (54.7%) of the children 5-17 years were caries-free in their permanent dentition. The occurrence of caries in the permanent dentition is clustered: A quarter of the children and adolescents ages 5 to 17 with at least one permanent tooth accounted for about 80% of the caries experienced in permanent teeth. Differences in caries experience were found among race and race-ethnicity subpopulations, and caries patterns for the primary and permanent dentition were dissimilar. Further analyses are needed to explore other potential determinants of caries in children.

Periodontal status in the United States, 1988-1991: prevalence, extent, and demographic variation

This paper reports estimates of the periodontal status of US population derived from data from Phase 1 of the Third National Health and Nutrition Examination Survey conducted by the National Institute of Dental Research from 1988-1991. A total of 7,447 dentate individuals 13 years of age and older, representing approximately 160.3 million civilian non-institutionalized Americans, received a periodontal assessment. Measurements of gingival bleeding, gingival recession level, periodontal pocket depth, and calculus were made by dental examiners. Assessments were made at the mesiobuccal and mid-buccal sites of all fully erupted permanent teeth present in two randomly selected quadrants, one maxillary and one mandibular. All data were weighted and standard errors calculated by special software to adjust for the effect of sample design. Although over 90% of persons 13 years of age or older had experienced some clinical loss of attachment (LA), only 15% exhibited more severe destruction (LA > or = 5 mm). Prevalence of moderate and severe LA and gingival recession increased with age, while prevalence of pockets > or = 4 mm or > or = 6 mm did not. These data suggest that the increasing prevalence of LA with age is more associated with increasing prevalence of recession than with changes in the prevalence of pockets or age. The extent or number of affected sites with advanced conditions for loss of attachment, pocket depth, or recession was not large for any age group. Differences in prevalence of moderate and severe loss of attachment, moderate and deep pockets, and recession were found among gender and race-ethnicity groups. Females exhibited better periodontal health than males, and non-Hispanic whites exhibited better periodontal health than either non-Hispanic blacks or Mexican-Americans.

Denture use and the technical quality of dental prostheses among persons 18-74 years of age: United States, 1988-1991

For persons without all or some of their natural teeth in one or both arches, the use of a complete or partial denture and the quality of the denture used are important aspects of their oral health and functioning. This report of prosthodontic findings from the first three years of the 1988-94 National Health and Nutrition Examination Survey (NHANES III-Phase 1) provides estimates of denture use among the US civilian non-institutionalized population 18-74 years of age, as well as seminal information on the technical quality of dental prostheses nationwide. NHANES III-Phase 1 prosthodontic findings indicated that about one in five persons 18-74 years of age wears a removable prosthodontic appliance of some type. Overall, removable prosthodontic appliances are worn disproportionately more often by women than by men, and less frequently by whites than by blacks. Comparisons among race-ethnicity categories indicate that Mexican-Americans are less likely to use dentures than either of their non-Hispanic counterparts. Analyses of prosthodontic evaluation data indicated that approximately 60% of denture users have at least one problem with a denture. These findings from the oral component of NHANES III-Phase 1 provide clear indications that, despite increasing trends in tooth retention, dependence on removable prosthodontic appliances is still a reality of life for millions of Americans.

Tooth retention and tooth loss in the permanent dentition of adults: United States, 1988-1991

While the overall prevalence of tooth loss and edentulism has been declining in the United States over the past several decades, important variations remain among subgroups of the population. Data from Phase 1 of the Third National Health and Nutrition Examination Survey (NHANES III) provide the most current estimates of the prevalence and distribution of tooth retention and tooth loss in the United States. Weighted analyses were conducted for all adults 18+ years of age (n=8,366) and for selected age, gender, and race-ethnicity groups. In 1988-91, 89.5% of the population was dentate, and 30.5% had retained all 28 teeth. The mean number of teeth retained was 21.1 for all adults and 23.5 for dentate persons. The most commonly retained teeth in the mouth were the six anterior teeth in the lower arch. Conversely, 10.5% of the population was edentulous. Partial edentulism was much more common in the upper arch than in the lower arch. The most commonly missing teeth were the first and second molars. Age was strongly related to every measure of tooth retention and tooth loss. Gender was not related to any of these measures, after adjustment for age. Race-ethnicity was consistently related to these measures, after adjustment for age and gender. In general, Mexican-Americans had the lowest and black non-Hispanics the highest rates of tooth loss. Future research needs to examine a wide range of potential correlates of tooth retention and tooth loss before we can understand the complex interplay among the personal, dental, and environmental factors influencing tooth retention and tooth loss in the United States.

Calcium activation of mitochondrial glycerol phosphate dehydrogenase restudied

cDNAs which encode the rat testis and pancreatic islet mitochondrial glycerol phosphate dehydrogenase (mGPD) (EC 1.1.99.5), the key enzyme of the glycerol phosphate shuttle, were recently cloned and sequenced and found to contain calmodulin-like calcium-binding sequences, thus explaining the widely observed calcium activation of the enzyme from many tissues of higher eukaryotes. mGPD activity and protein, as judged from Western analysis, appear to be most abundant in testis and pancreatic islets in the rat. mGPD is known to be located within the inner mitochondrial membrane. At a physiologic concentration of glycerol phosphate (75 microM), half maximal activity of Triton X-100-solubilized testis mGPD was seen in the presence of 0.1-0.25 microM free calcium. Calcium (10(-6)-10(-5) M) lowered the Km of mGPD from 2.5 mM glycerol phosphate (islet mGPD) and 3.2 mM glycerol phosphate (testis mGPD) to 0.4 mM glycerol phosphate. Calcium activation of mGPD from both testis and islets was not prevented by calmodulin inhibitors, which is consistent with mGPD possessing regions that can mediate its own activation by calcium. 45Calcium overlay experiments, in which proteins were separated by SDS-polyacrylamide gel electrophoresis, blotted onto nitrocellulose membranes, and probed with 45Ca, showed that mGPD is a major calcium-binding protein in testis mitochondrial membranes. A hydropathy plot suggested that the mature mGPD protein has three transmembrane helices. The first membrane-spanning region coincides with the FAD site and thus this site is placed within the membrane. The hydropathy analysis indicated that the calcium-binding region and the putative glycerol phosphate-binding site lie outside the membrane exposed to the cytosolic environment. This is consistent with earlier biochemical evidence which indicated that these sites are situated outside the membrane (M. Klingenberg, Eur. J. Biochem. 13, 247-252, 1970). This suggests that cytosolic calcium can regulate mGPD activity. Since simultaneous oscillations in electrical activity, cytosolic calcium, glycolysis, and insulin release occur in the pancreatic beta cell, mGPD activity might also fluctuate and allow the glycerol phosphate shuttle to participate in glycolytic oscillations.

Selected restoration and tooth conditions: United States, 1988-1991

The DMF index provides one source of information on past and present dental caries experience; however, important limitations hinder its ability to characterize fully the impact of dental caries. The purpose of this paper is to describe a measure of selected restoration and tooth conditions that supplements information from the DMF index and to report on the application of this measure as part of the Third National Health and Nutrition Examination Survey, Phase 1, conducted between 1988 and 1991. Data from this survey were used to estimate the prevalence and severity of selected disaggregated physical and biological oral conditions among dentate adults aged 18 to 74 years. Trained, standardized, and calibrated dentist examiners assessed 28 permanent teeth or tooth spaces for each of 6,767 subjects. Teeth or tooth spaces were classified based on criteria for: defective intracoronal restorations, crowns, or bridges; gross loss of tooth structure associated with a restoration; pulpal involvement; or retained roots. Approximately 40.5%, or 61.6 million, dentate adults had at least one tooth or tooth space that met the criteria. Among all persons, an average of 0.9 teeth or tooth spaces met the criteria for at least one category. Adults with at least one scored tooth or tooth space had an average of 2.2 such teeth or tooth spaces. Data from this assessment supplement information available from the DMF index to provide a broader profile of the impact of dental caries on permanent teeth of US adults.

The impact of recent changes in the epidemiology of dental caries on guidelines for the use of dental sealants

This paper reviews recent changes in the epidemiology of dental caries and assesses their potential impact on the diagnosis and management of the disease and the planning and operation of sealant programs. These changes, such as the decline in caries and slowing of the rate of progression of the disease, have important implications for diagnosing and treating incipient lesions, predicting caries risk, and conducting effective disease preventive programs. Traditional paradigms for restoring carious lesions are being replaced by newer strategies that emphasize disease prevention and conservation of tooth structure. The search continues for the identification of practical models for predicting caries risk at the individual level. This paper describes a method useful for targeting resources in sealant placement programs by enabling one to determine the relative effectiveness of sealing alternative tooth surfaces in the oral cavity. One guide serves as a widely adopted manual for those who use or intend to use dental sealants in caries prevention programs. This paper provides a brief review of that document, "Preventing Pit and Fissure Caries: A Guide to Sealant Use," as well as guidelines for sealant utilization provided by the American Dental Association, and information regarding dental sealant programs under Medicaid. The final portion of the paper provides a synthesis of the epidemiology reviewed and summarizes the implications of findings for sealant programs.

Immunogenetic, clinical, and demographic characterization of childhood type I diabetes in New Zealand

OBJECTIVE

To examine the relationship between genetic susceptibility alleles and islet cell antibodies (ICAs) in type I diabetes.

RESEARCH DESIGN AND METHODS

The human leukocyte antigen (HLA)-DQB1 alleles and ICA levels of all incident type I diabetic cases in patients < 20 years of age diagnosed in 1990 and 1991 in Canterbury, New Zealand, were determined.

RESULTS

The mean annual incidence rate for type I diabetes over the 24 months was 19.0/100,000 patient-years (95% confidence interval [CI] 13.5-26.0/100,000), which was considerably higher than rates observed between 1982 and 1989 (11.7/100,000; 95% CI 9.6-14.3/100,000). ICAs > or = 10 Juvenile Diabetes Foundation units (JDF U) were present in 84.6% of the subjects, but there was a higher prevalence of ICA-negative (ICA-) subjects among those diagnosed during the winter months. The frequencies of the susceptibility allele DQB1*0302 and susceptibility genotype 0302/0201 were 71.8% and 43.5%, respectively. Subjects with 0302 tended to be younger (mean age 8.3 +/- 5.1 years) than those with nonsusceptibility types (mean age 11.8 +/- 4.7 years, P = 0.056). The probability of being ICA positive (ICA+) was not significantly different between subjects with allele 0302 (85.7%) and those without it (81.8%). All seven patients negative for ICA were homozygous for DQB1 nonaspartate-57. There was no clustering of the immunogenetic markers with demographic and clinical characteristics apart from age at diagnosis.

CONCLUSIONS

No direct relationship was observed between DQB1-defined genetic susceptibility and ICA at diagnosis, suggesting that variations at the DQB1 locus are not linked to the expression of this autoimmune marker of beta-cell destruction.

Improved periodontal status through self-assessment. A 2-year longitudinal study in teenagers

Short-term success of the use of self-assessment for motivating adults to improve their oral health status has been reported. The purpose of this trial was to evaluate the long-term effectiveness of two self-assessment strategies, one focused on gingival bleeding (group I) and another focused on plaque (group II). At baseline, 493 14- and 15-year-olds were assigned randomly to a group. Each subject was given a manual describing one of the self-assessment processes. Dental hygienists provided standardized classroom based instruction and two weeks later, individualized counselling. Examinations were conducted at baseline 6, 12, 18 and 24 months for gingival bleeding on probing, plaque, calculus, and probing depth; and at baseline and 24 months for recession and decayed, missing and filled surfaces (DMFS). Following the 12-month examination, subjects received an oral prophylaxis and individual counselling. The results revealed no statistically significant differences between groups for any clinical parameter at the final examination. However, the mean number of sites with gingival bleeding decreased steadily from baseline to 24 months with a 59% decrease and 55% decrease for groups I and II, respectively. This study suggests that self-assessment approaches can be effective in improving the long-term periodontal health status of teenagers.

The oral health of U.S. Hispanics: evaluating their needs and their use of dental services

Data from the 1985-1986 National Survey of Oral Health in U.S. Adults and Seniors showed that the oral health of Hispanic American adults and seniors was comparable to that of black adults and seniors. White adults and seniors had better oral health than their minority counterparts for all measures observed and were better able to afford dental care.

How fee and insurance changes could affect dentistry: results from a microsimulation model

Dentists have become concerned about the possible impact of reductions in dental insurance coverage. The authors used a microsimulation model of the dental sector to assess the potential impact of reductions in the percentage of Americans with dental insurance, in universal dental insurance coverage for children and in fees paid to dentists for their services. The model predicted that reductions in dental insurance coverage would reduce per capita dental expenditures, but that the impact would not be large. Fee reductions had the greatest impact on dental expenditures of any change simulated by the model.

The sequence of a human mitochondrial glycerol-3-phosphate dehydrogenase-encoding cDNA

A 2618-bp cDNA that encodes the human mitochondrial glycerol-3-phosphate dehydrogenase has been isolated from a HeLa cell cDNA library and the nucleotide sequence determined. An open reading frame encodes a protein of 727 amino acids that is 96% similar to the rat protein and, like the rat protein, contains sites homologous to the Ca(2+)-binding sites of calmodulin, as well as FAD- and putative glycerol-phosphate-binding sites.

Attitudes and knowledge regarding contraception and prepregnancy counselling in insulin dependent diabetes

AIMS

To assess knowledge and attitudes of women with insulin dependent diabetes to contraception, prepregnancy planning, and genetic risk.

METHOD

Women with insulin dependent diabetes, aged 18 to 40, were identified from a population-based register of insulin users in North Canterbury. Participating subjects underwent a structured face to face interview, assessing current contraceptive practices and their knowledge and attitudes to the areas outlined above.

RESULTS

One hundred and twenty four women, representing 86% of eligible women, agreed to participate. Eighty five subjects were using some form of contraception. The most popular choices were the combined oral contraceptive pill (35%), the progesterone only pill (12%), condoms (24%), vasectomy (12%) and tubal ligation (12%). All subjects recognised the importance of good blood glucose control during pregnancy. Thirty nine percent of subjects using contraception avoided the combined oral contraceptive pill because of concerns about metabolic and vascular side effects. Only 52% of subjects knew the correct figure for genetic risk of passing insulin dependent diabetes on to an offspring.

CONCLUSIONS

Patient education regarding the need for prepregnancy planning in women with insulin dependent diabetes appeared adequate and the percentage of subjects using contraception was higher than that described in overseas diabetic populations. Over a third of subjects were however concerned about the risks of contraceptive options in insulin dependent diabetes, particularly with regard to the use of the combined oral contraceptive pill. This finding suggests that discussion about the advantages and disadvantages of contraceptive choices should be an integral part of patient education for women with insulin dependent diabetes mellitus of child-bearing age. Knowledge about genetic risk was inadequate in half the subjects interviewed, and this area of patient education could also be improved.

Stimulated parotid salivary flow rates in normotensive, hypertensive, and hydrochlorothiazide-medicated

Stimulated parotid salivary flow rates were compared in elderly normotensive, hypertensive, and controlled hypertensive African-Americans, the latter group taking hydrochlorothiazide (HCTZ). The normotensive group consisted of 15 healthy unmedicated subjects with systolic blood pressures of less than 150 mm Hg and diastolic pressures less than 90 mm Hg. The hypertensive group consisted of 10 unmedicated subjects with systolic pressures greater than 160 mm Hg and diastolic pressures greater than 100 mm Hg. The controlled hypertensive group consisted of 20 subjects taking HCTZ (50 mg, daily) with controlled blood pressures similar to the normotensive control group. Stimulated parotid salivary samples were collected from each subject. A 2% citrate solution applied to the dorsum of the tongue was used for stimulation. The results showed no significant differences in stimulated parotid flow rates between normotensive and uncontrolled hypertensive subjects. However, the medicated, controlled hypertensive subjects had a significant reduction of stimulated parotid salivary flow rates compared to both the normotensive and hypertensive groups.

Retinoic acid suppression of loricrin expression in reconstituted human skin cultured at the liquid-air interface

Retinoids have been shown to modulate the expression of proteins involved in epidermal differentiation. To examine this effect in an in vitro skin model, we evaluated the effect of retinoic acid on the expression of two cell envelope proteins, loricrin and involucrin, and an early marker of epidermal differentiation, keratin 1, in a reconstituted human skin equivalent cultured at the liquid-air interface. Retinoic acid, a known inhibitor of keratinization in monolayer and raft cultures, was evaluated for its ability to alter the expression and distribution of these markers of epidermal differentiation. Retinoic acid (10(-6) M) suppressed loricrin expression in skin cultures as determined by both protein and mRNA analysis. In contrast, no inhibition of involucrin or K1 expression was observed at the protein level at the same retinoic acid concentration. However, some suppression of K1 mRNA transcription was observed in retinoic acid-treated cultures. These results demonstrate that in differentiating cultures of reconstituted human skin, loricrin expression is markedly inhibited by retinoids, K1 less so, and involucrin not at all.

Comparison of stimulated parotid salivary gland flow rates in normotensive and hypertensive persons

Although hypertension is a prevalent condition among the elderly, little is known with respect to the influence of hypertension on oral health and function. Therefore a study was conducted that compared stimulated parotid salivary flow rates in elderly persons (65 years and older) from two diverse populations who are normotensive, mild, and severe hypertensive. The normotensive group consisted of 45 healthy subjects with systolic blood pressures of less than 140 mm Hg and diastolic pressures less than 90 mm Hg. The mildly hypertensive group consisted of 14 otherwise healthy subjects with either systolic pressures greater than 140 mm Hg or diastolic pressures greater than 90 mm Hg. The severely hypertensive group consisted of 10 otherwise healthy subjects with either systolic pressures greater than 180 mm Hg and/or diastolic pressures greater than 100 mm Hg. All three groups were not taking any prescription or nonprescription medications. Samples of 2% citrate-stimulated parotid saliva were collected from each subject. The results showed no significant differences in stimulated parotid flow between normotensive, mildly hypertensive, and severely hypertensive subjects. These results suggest that hypertension per se has no influence on stimulated parotid salivary gland flow rates in otherwise healthy, elderly unmedicated white and African-American persons.

Sequence of rat mitochondrial glycerol-3-phosphate dehydrogenase cDNA. Evidence for EF-hand calcium-binding domains

The FAD-dependent, mitochondrial glycerol-3-phosphate dehydrogenase (EC 1.1.99.5) is an essential component of the glycerol phosphate shuttle and is abundant in the pancreatic insulin cell, skeletal muscle, and brain. Although DNA clones for this enzyme and its homologues have been isolated from bacteria and yeast, it has never been cloned from a higher eukaryote. We have cloned and sequenced cDNAs encoding the rat mitochondrial glycerol-3-phosphate dehydrogenase. The longest cDNA (2337 base pairs) encodes a deduced protein of 727 amino acids that shows strong homology to the yeast and bacterial FAD-dependent glycerol phosphate dehydrogenases. The amino terminus of the purified mature protein was sequenced and shows identity with the deduced amino acid sequence beginning with residue 43. The 42 preceding amino acids are consistent with a mitochondrial leader peptide. A highly conserved FAD-binding domain and conserved regions possibly involved with glycerol phosphate binding are present. An unexpected finding was the homology of the deduced protein to calmodulin. Analysis of the deduced protein sequence shows a region near the carboxyl terminus containing two sequences homologous to "EF-hand" calcium-binding domains that are not present in the shorter yeast and bacterial homologues. The second of these domains appears to have features compatible with considerable affinity for calcium, whereas the first does not. The finding of a potential calcium-binding region is consistent with the known enhancement by calcium of the mammalian enzyme activity at low substrate concentrations and the lack of a requirement for calmodulin. This is the first report of EF-hands in a metabolic enzyme or in a mitochondrial protein.