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A R Patterson

Publications and source records attributed to A R Patterson.

8 recordsLinked to original sources
PubMed1999

His(15) of subunit a of the Escherichia coli ATP synthase is important for the structure or assembly of the membrane sector F(o).

Approximately 37 amino acids at the amino-terminus of subunit a of the Escherichia coli ATP synthase are found localized to the periplasm. Results indicate that a single amino acid substitution, H15D, disrupts assembly of subunit a and causes a loss of ATP synthase function. In this study, a conserved region of nine amino acids, 11-19, was initially mutagenized randomly, generating no mutants that could grow on succinate-minimal medium. Subsequent mutagenesis, confined to residues His(14), His(15), and Asn(17), indicated that constructs containing H15D were the most deleterious. Four single mutants were constructed and analyzed: H15A, H14D, H15A, and H15D. Only H15D was significantly impaired, with respect to ATP-driven proton translocation, passive proton permeability through F(o), and sensitivity of membrane-bound ATPase to DCCD. Immunoblot analysis indicated very low levels of subunit a from H15D. Cysteine mutations were constructed at positions 14, 15, 17, and 18. Residues 14, 15, and 17 were shown to be accessible in the periplasmic space, while residue 18 was not, indicating that this region was stably folded. While both His(14) and His(15) are conserved among a group of bacteria, results presented here indicate that they are not equivalent, and that a specific role for His(15) in the assembly or structure of the ATP synthase is supported.

Amino Acid Sequence↗
PubMed1998

Insertion scanning mutagenesis of subunit a of the F1F0 ATP synthase near His245 and implications on gating of the proton channel.

Subunit a of the E. coli F1F0 ATP synthase was probed by insertion scanning mutagenesis in a region between residues Glu219 and His245. A series of single amino acid insertions, of both alanine and aspartic acid, were constructed after the following residues: 225, 229, 233, 238, 243, and 245. The mutants were tested for growth yield, binding of F1 to membranes, dicyclohexylcarbodiimide sensitivity of ATPase activity, ATP-driven proton translocation, and passive proton permeability of membranes stripped of F1. Significant loss of function was seen only with insertions after positions 238 and 243. In contrast, both insertions after residue 225 and the alanine insertion after residue 245 were nearly identical in function to the wild type. The other insertions showed an intermediate loss of function. Missense mutations of His245 to serine and cysteine were nonfunctional, while the W241C mutant showed nearly normal ATPase function. Replacement of Leu162 by histidine failed to suppress the 245 mutants, but chemical rescue of H245S was partially successful using acetate. An interaction between Trp241 and His245 may be involved in gating a "half-channel" from the periplasmic surface of F0 to Asp61 of subunit a.

Amino Acid Sequence↗
PubMed1987

Effect of type of anesthesia on blood loss at cesarean section.

Halogenated anesthetic agents have been used to supplement nitrous oxide during balanced general anesthesia for cesarean delivery to decrease maternal awareness. However, these agents can interfere with uterine contractility and hence have the potential to increase blood loss at the time of cesarean section. To ascertain the effect of the addition of halogenated anesthetic agents for cesarean section anesthesia versus conduction or a simple balanced general anesthetic, we retrospectively assessed three aspects that may reflect operative blood loss at the time of cesarean section. Significantly more women whose balanced general anesthesia for cesarean section was supplemented with a halogenated agent (usually 0.5% halothane) versus those with a conduction or balanced general anesthetic required transfusion therapy, had a postpartum hematocrit less than 30 vol% and had a decrease in the pre- to postdelivery hematocrit of at least 8 vol %. The addition of halogenated anesthetic agents to a balanced nitrous oxide anesthesia for the purpose of decreased maternal awareness must be weighed against the risk incurred from the increased requirement for blood replacement and/or from postpartum anemia.

Anesthesia, Conduction↗