Article Watch,April 2010

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information about articles they feel are important and useful to Clive Slaughter, MCG-UGA Medical Partnership, 279 William St., Athens, GA 30607-1777, USA. Tel.: (706) 369-5945: Fax: (706) 369-5936; E-mail: ude.gcm.liam@rethgualsc; or to any member of the editorial board. Article summaries reflect the reviewer''s opinions and not necessarily those of the association.     

Article Watch, April 2012

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information on articles they feel are important and useful to Clive Slaughter, Georgia Health Sciences University-University of Georgia Medical Partnership, 279 William St., Athens GA 30607-1777. Phone: 706-369-5945; Fax: 706-369-5936; E-mail: ude.agu@thgualsc; or to any member of the editorial board. Article summaries reflect the reviewer''s opinions and not necessarily those of the association.     

Article Watch: April 2016

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information on articles they feel are important and useful to Clive Slaughter, MCG-UGA Medical Partnership, 1425 Prince Ave., Athens, GA 30606, USA; Tel: (706) 713-2216; Fax: (706) 713-2221; E-mail: cslaught@uga.edu, or to any member of the editorial board. Article summaries reflect the reviewer’s opinions and not necessarily those of the association.     

Article Watch: December 2015

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information on articles they feel are important and useful to: Clive Slaughter, GRU-UGA Medical Partnership, 1425 Prince Ave., Athens, GA 30606, USA. Tel: (706) 713-2216; Fax: (706) 713-2221; E-mail: cslaught@uga.edu; or to any member of the editorial board. Article summaries reflect the reviewer’s opinions and not necessarily those of the association.     

Article Watch: July 2021

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information on articles they feel are important and useful to Clive Slaughter, MCG-UGA Medical Partnership, 1425 Prince Avenue, Athens GA 30606. Tel; (706) 713-2216: Fax; (706) 713-2221: Email; cslaught@uga.edu or to any member of the editorial board. Article summaries reflect the reviewer’s opinions and not necessarily those of the Association.     

Article Watch: July 2016

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information on articles they feel are important and useful to Clive Slaughter, MCG-UGA Medical Partnership, 1425 Prince Ave., Athens, GA 30606, USA. Tel: (706) 713-2216; Fax: (706) 713-2221; E-mail: cslaught@uga.edu, or to any member of the editorial board. Article summaries reflect the reviewer''s opinions and not necessarily those of the association.     

Article Watch: September 2021

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information on articles they feel are important and useful to Clive Slaughter, AU-UGA Medical Partnership, 1425 Prince Avenue, Athens GA 30606. Phone: (706) 713-2216; Fax: (706) 713-2221; E-mail: ude.agu@thgualsc or to any member of the editorial board. Article summaries reflect the reviewer''s opinions and not necessarily those of the Association.     

Article Watch: April 2021

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information on articles they feel are important and useful to Clive Slaughter, MCG-UGA Medical Partnership, 1425 Prince Ave., Athens GA 30606, USA. Tel: (706) 713-2216; Fax: (706) 713-2221; E-mail; ude.agu@thgualsc, or to any member of the editorial board. Article summaries reflect the reviewer’s opinions and not necessarily those of the Association.     

Article Watch: April 2014

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information on articles they feel are important and useful to Clive Slaughter, Georgia Regents University/University of Georgia Medical Partnership, 1425 Prince Ave., Athens, GA 30606, USA (Phone: 706-713-2216; Fax: 706-713-2221; E-mail; ude.agu@thgualsc), or to any member of the editorial board. Article summaries reflect the reviewer''s opinions and not necessarily those of the association.     

Article Watch: September 2013

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information on articles they feel are important and useful to Clive Slaughter, GRU-UGA Medical Partnership, 1425 Prince Ave., Athens, GA 30606; Phone: 706-713-2216; Fax: 706-713-2221; E-mail: ude.agu@thgualsc; or to any member of the editorial board. Article summaries reflect the reviewer''s opinions and not necessarily those of the association.     

Article Watch,December 2013

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information on articles they feel are important and useful to Clive Slaughter, Georgia Regents University–University of Georgia Medical Partnership, 1425 Prince Ave., Athens, GA 30606, USA. Phone: 706-713-2216; Fax: 706-713-2221; E-mail: ude.agu@thgualsc; or to any member of the editorial board. Article summaries reflect the reviewer''s opinions and not necessarily those of the association.     

Article Watch: September 2014

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information on articles they feel are important and useful to Clive Slaughter, Georgia Regents University-University of Georgia Medical Partnership, 1425 Prince Ave., Athens, GA 30606, USA. Phone: 706-713-2216; Fax: 706-713-2221; E-mail: ude.agu@thgualsc; or to any member of the Editorial Board. Article summaries reflect the reviewer''s opinions and not necessarily those of the association.     

Article Watch: September 2015

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information on articles they feel are important and useful to Clive Slaughter, Georgia Regents University-University of Georgia Medical Partnership, 1425 Prince Ave., Athens, GA 30606, USA. Phone: 706-713-2216; Fax: 706-713-2221; E-mail: ude.agu@thgualsc; or to any member of the Editorial Board. Article summaries reflect the reviewer’s opinions and not necessarily those of the association.     

Article Watch: July 2014

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information on articles they feel are important and useful to Clive Slaughter, Georgia Regents University-University of Georgia Medical Partnership, 1425 Prince Ave., Athens, GA 30606, USA. Phone: 706-713-2216; Fax: 706-713-2221; E-mail: ude.agu@thgualsc; or to any member of the Editorial Board. Article summaries reflect the reviewer''s opinions and not necessarily those of the association.     

Article Watch: July 2015

This column highlights recently published articles that are of interest to the readership of this publication. We encourage ABRF members to forward information on articles they feel are important and useful to Clive Slaughter, Georgia Regents University-University of Georgia Medical Partnership, 1425 Prince Ave., Athens, GA 30606, USA. Phone: 706-713-2216; Fax: 706-713-2221; E-mail: ude.agu@thgualsc; or to any member of the Editorial Board. Article summaries reflect the reviewer’s opinions and not necessarily those of the association.     

Increase of hybrids in yeast electrofusion by mitochondrial mutations

Yeast mitochondria were found to affect the zeta-potential of protoplasts, resulting in electrofusion of membrane behavior. For modeling purposes, two fusion systems were investigated: (1) parent yeasts of Saccharomyces cerevisiae G706 (rho(+)) x O708-11-16A (rho(+)), with zeta-potentials of -10 to -27 mV and -28 to -45 mV, depending on MgCl(2) concentration in the medium, respectively; and (2) parent yeasts of S. cerevisiae G706-1 (rho(-)) x O708-11-16A (rho(+)), with zeta-potentials of -30 to -60 mV, depending on MgCl(2). Yields of the hybrids in system (2) were over 100-fold higher than those in system (1). Thus, regulation of yeast electrofusion was found to be possible by mitochondrial mutations.     

Structure of the O-antigen polysaccharide present in the lipopolysaccharide of Cronobacter dublinensis (subspecies lactaridi or lausannensis) HPB 3169

Cronobacter dublinensis (formerly Enterobacter sakazakii) HPB 3169 is a pathogenic Gram-negative bacterium that produces a smooth-type lipopolysaccharide in which the antigenic O-polysaccharide component was determined to be a repeating pentasaccharide unit composed of L-rhamnose; 2-acetamido-2-deoxy-D-glucose; 3,6-dideoxy-3-(R)-3-hydroxybutyramido-D-glucose; and 3-deoxy-manno-oct-2-ulosonic acid in the respective molar ratio 2:1:1:1. Chemical and 2D NMR analyses of the O-polysaccharide and a pentasaccharide derived by the mild acid hydrolysis of the ketosyl linkage of the Kdo (3-deoxy-D-manno-2-octulosonic acid) residue in the O-polysaccharide established that the O-antigen is a high molecular mass unbranched polymer of a repeating pentasaccharide unit and has the structure [see formula in text] where Bu is a (R)-3-hydroxybutanoyl substituent. The O-antigen is structurally similar to that of the recently reported Cronobacter sakazakii strain G706 (designated as serotype O5), except that in strain G706 the d-Qui3N is in its N-acetyl form, in contrast to its presence as a 3-deoxy-3-(R)-3-hydroxybutyramido derivative in the C. sakazakii HPB 3169 strain O-antigen.     

Dissecting requirements for auto-inhibition of actin nucleation by the formin, mDia1

The mammalian formin, mDia1, is an actin nucleation factor. Experiments in cells and in vitro show that the N-terminal region potently inhibits nucleation by the formin homology 2 (FH2) domain-containing C terminus and that RhoA binding to the N terminus partially relieves this inhibition. Cellular experiments suggest that potent inhibition depends upon the presence of the diaphanous auto-regulatory domain (DAD) C-terminal to FH2. In this study, we examine in detail the N-terminal and C-terminal regions required for this inhibition and for RhoA relief. Limited proteolysis of an N-terminal construct from residues 1-548 identifies two stable truncations: 129-548 and 129-369. Analytical ultracentrifugation suggests that 1-548 and 129-548 are dimers, whereas 129-369 is monomeric. All three N-terminal constructs inhibit nucleation by the full C terminus. Although inhibition by 1-548 is partially relieved by RhoA, inhibition by 129-548 or 129-369 is RhoA-resistant. At the C terminus, DAD deletion does not affect nucleation but decreases inhibitory potency of 1-548 by 20,000-fold. Synthetic DAD peptide binds both 1-548 and 129-548 with similar affinity and partially relieves nucleation inhibition. C-terminal constructs are stable dimers. Our conclusions are as follows: 1) DAD is an affinity-enhancing motif for auto-inhibition; 2) an N-terminal domain spanning residues 129-369 (called DID for diaphanous inhibitory domain) is sufficient for auto-inhibition; 3) a dimerization region C-terminal to DID increases the inhibitory ability of DID; and 4) DID alone is not sufficient for RhoA relief of auto-inhibition, suggesting that sequences N-terminal to DID are important to RhoA binding. An additional finding is that FH2 domain-containing constructs of mDia1 and mDia2 lose >75% nucleation activity upon freeze-thaw.     

Conserved tyrosine-369 in the active site of Escherichia coli copper amine oxidase is not essential.

Copper amine oxidases are homodimeric enzymes that catalyze two reactions: first, a self-processing reaction to generate the 2,4,5-trihydroxyphenylalanine (TPQ) cofactor from an active site tyrosine by a single turnover mechanism; second, the oxidative deamination of primary amine substrates with the production of aldehyde, hydrogen peroxide, and ammonia catalyzed by the mature enzyme. The importance of active site residues in both of these processes has been investigated by structural studies and site-directed mutagenesis in enzymes from various organisms. One conserved residue is a tyrosine, Tyr369 in the Escherichia coli enzyme, whose hydroxyl is hydrogen bonded to the O4 of TPQ. To explore the importance of this site, we have studied a mutant enzyme in which Tyr369 has been mutated to a phenylalanine. We have determined the X-ray crystal structure of this variant enzyme to 2.1 A resolution, which reveals that TPQ adopts a predominant nonproductive conformation in the resting enzyme. Reaction of the enzyme with the irreversible inhibitor 2-hydrazinopyridine (2-HP) reveals differences in the reactivity of Y369F compared with wild type with more efficient formation of an adduct (lambda(max) = 525 nm) perhaps reflecting increased mobility of the TPQ adduct within the active site of Y369F. Titration with 2-HP also reveals that both wild type and Y369F contain one TPQ per monomer, indicating that Tyr369 is not essential for TPQ formation, although we have not measured the rate of TPQ biogenesis. The UV-vis spectrum of the Y369F protein shows a broader peak and red-shifted lambda(max) at 496 nm compared with wild type (480 nm), consistent with an altered electronic structure of TPQ. Steady-state kinetic measurements reveal that Y369F has decreased catalytic activity particularly below pH 6.5 while the K(M) for substrate beta-phenethylamine increases significantly, apparently due to an elevated pK(a) (5.75-6.5) for the catalytic base, Asp383, that should be deprotonated for efficient binding of protonated substrate. At pH 7.0, the K(M) for wild type and Y369F are similar at 1.2 and 1.5 microM, respectively, while k(cat) is decreased from 15 s(-1) in wild type to 0.38 s(-1), resulting in a 50-fold decrease in k(cat)/K(M) for Y369F. Transient kinetics experiments indicate that while the initial stages of enzyme reduction are slower in the variant, these do not represent the rate-limiting step. Previous structural and solution studies have implicated Tyr369 as a component of a proton shuttle from TPQ to dioxygen. The moderate changes in kinetic parameters observed for the Y369F variant indicate that if this is the case, then the absence of the Tyr369 hydroxyl can be compensated for efficiently within the active site.