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Morphologic features of the mandible are influenced by the genes of each individual. Mandible size is important to orthodontists because the mandible is the mechanism by which the lower face influences facial esthetics and dental function. To date, no biological marker has been identified that indicates eventual mandible size. This study aimed to correlate the expression of DLX5 , DLX6 , EDN1 , HAND2 , PRRX1, and MSX1 to mandible size. Fifty-nine orthodontic patients aged >6 years who had available cephalometric radiographs were studied. Patients were classified on the basis of condylion-to-gnathion measurements. Messenger RNA was isolated from saliva and subjected to real-time quantitative polymerase chain reaction. Threshold cycle values for subjects with small mandibles (>1 standard deviation [SD] from the mean) had the least expression of DLX6 and MSX1. Threshold cycle values for subjects with large mandibles (>1 SD) had less expression of DLX6 and MSX1 than subjects within 1 SD but more than those with small mandibles. DLX6 and MSX1 are related to mandible development and size. This finding could be used to improve treatment planning for medical and dental professionals seeking to understand the impact of genetics on bone growth. • Fifty-nine orthodontic patients aged >6 years were studied. • DLX6 and MSX1 expression could be used as biomarkers of mandible size. • DLX6 and MSX1 expression help differentiate large and small mandibles. • DLX5 , HAND2 , EDN1, and PRRX1 expression are not biomarkers of mandibular size. • Saliva is a useful, noninvasive biofluid to measure biomarkers. [ABSTRACT FROM AUTHOR]

Discusses teaching social studies using public issues to develop student understanding. Describes identification of issues, justification and clarification of positions, and the discussion process. Suggests that selection of issues should be based on the importance of the issues to society and their significance for teachers and students. (DK)

Drawn from the postmodern view of nature, this essay discusses the distinction between two kinds of knowing (grounded and technical) and explores the implications of this distinction for selecting and teaching science curricula. The concept of presence needs to be incorporated into a curriculum overly concerned with the observing mind and external facts. Includes three references. (MLH)

The SecA nanomotor promotes protein translocation in eubacteria by binding both protein cargo and the protein-conducting channel and by undergoing ATP-driven conformation cycles that drive this process. There are conflicting reports about whether SecA functions as a monomer or dimer during this dynamic process. Here we reexamined the roles of the amino and carboxyl termini of SecA in promoting its dimerization and functional state by examining three secA mutants and the corresponding proteins: SecA[DELTA]8 lacking residues 2 to 8, SecA[DELTA]11 lacking residues 2 to 11, and SecA[DELTA]11/N95 lacking both residues 2 to 11 and the carboxyl- terminal 70 residues. We demonstrated that whether SecA[DELTA]11 or SecA[DELTA]11/N95 was functional for promoting cell growth depended solely on the vivo level of the protein, which appeared to govern residual dimerization. All three SecA mutant proteins were defective for promoting cell growth unless they were highly overproduced. Cell fractionation revealed that SecA[DELTA]11 and SecA[DELTA]11/N95 were proficient in membrane association, although the formation of integral membrane SecA was reduced. The presence of a modestly higher level of SecAAll/N95 in the membrane and the ability of this protein to form dimers, as detected by chemical cross-linking, were consistent with the higher level of secA expression and better growth of the SecAAll/N95 mutant than of the SecA[DELTA]11 mutant. Biochemical studies showed that SecAAll and SecAAll/N95 had identical dimerization defects, while SecA[DELTA]8 was intermediate between these proteins and wild-type SecA in terms of dimer formation. Furthermore, both SecA[DELTA]11 and SecA[DELTA]11/N95 were equally defective in translocation ATPase specific activity. Our studies showed that the nonessential carboxyl-terminal 70 residues of SecA play no role in its dimerization, while increasing the truncation of the amino-terminal region of SecA from 8 to 11 residues results in increased defects in SecA dimerization and poor in vivo function unless the protein is highly over-expressed. They also clarified a number of conflicting previous reports and support the essential nature of the SecA dimer.

SecA facilitates protein transport across the eubacterial plasma membrane by its association with cargo proteins and the SecYEG translocon, followed by ATP-driven conformational changes that promote protein translocation in a stepwise manner. Whether SecA functions as a monomer or a dimer during this process has been the subject of considerable controversy. Here we utilize cysteine-directed mutagenesis along with the crystal structure of the SecA dimer to create a cross-linked dimer at its subunit interface, which was normally active for in vitro protein translocation.

SecA is an ATPase and motor protein that drives protein translocation across the bacterial plasma membrane. In Escherichia coli SecA levels are regulated by the secretion needs of the cell utilizing secM, which encodes a secreted protein. Previous studies demonstrated that this regulation requires a translational pause within secM, whose duration regulates the accessibility of the secA Shine-Dalgarno sequence on secM secA mRNA. Here we provide evidence that translocon 'pulling' of nascent SecM is what regulates the duration of the secM translational pause, and thus secA expression levels, thereby providing direct support for this model.

Research has been conducted on the atypical secM signal peptide. The characterization of this peptide has been carried out and the results demonstrate that the peptide's amino-terminal and hydrophobic core regions have different functions.

Results show that out of the seven tryptophan residues in the C-domain of SecA protein, three residues exhibit fluorescence signal and different degrees of solvent accessibility. Data also indicate that the residues contribute to the spectoscopic changes due to endothermic transition or associated phospholipids or signal peptide binding.

Research has been conducted on the plasmid family of Borrelia burgdorferi packaged into a bacteriophage particle. Identification and characterization of a nonstructural product involved in the bacteriophage function from spirochete bacteriophage have been examined.