5 research outputs found
FIGURES 143–150. 143–148 in Taxonomy of the Proisotoma complex. Redefinition of genera and description of new species of Scutisotoma and Weberacantha (Collembola, Isotomidae)
No full textFIGURES 143–150. 143–148, Scutisotoma nicksmeti sp.n. 143, posterior side of furca; 144, dens, lateral; 145, PAO and ocelli; 146, chaetotaxy of Abd.V; 147, lateral sensillum and microsensillum on Abd.III (p-chaetae connected); 148, medial and lateral pairs of sensilla on Abd.III (s: sensillum, ms: microsensillum); 149–150, S. tianshanica. 149, dens, lateral; 150, medial and lateral pairs of sensilla on Abd.V (s1–4: accp1–4 sensilla).Published as part of Potapov, Mikhail, Babenko, Anatoly & Fjellberg, Arne, 2006, Taxonomy of the Proisotoma complex. Redefinition of genera and description of new species of Scutisotoma and Weberacantha (Collembola, Isotomidae), pp. 1-74 in Zootaxa 1382 (1) on page 54, DOI: 10.11646/zootaxa.1382.1.1, http://zenodo.org/record/507146
Development of a Rubredoxin-Type Center Embedded in a <i>de Dovo</i>-Designed Three-Helix Bundle
No full textProtein design is
a powerful tool for interrogating the basic requirements
for the function of a metal site in a way that allows for the selective
incorporation of elements that are important for function. Rubredoxins
are small electron transfer proteins with a reduction potential centered
near 0 mV (vs normal hydrogen electrode). All previous attempts to
design a rubredoxin site have focused on incorporating the canonical
CXXC motifs in addition to reproducing the peptide fold or using flexible
loop regions to define the morphology of the site. We have produced
a rubredoxin site in an utterly different fold, a three-helix bundle.
The spectra of this construct mimic the ultraviolet–visible,
Mössbauer, electron paramagnetic resonance, and magnetic circular
dichroism spectra of native rubredoxin. Furthermore, the measured
reduction potential suggests that this rubredoxin analogue could function
similarly. Thus, we have shown that an α-helical scaffold sustains
a rubredoxin site that can cycle with the desired potential between
the Fe(II) and Fe(III) states and reproduces the spectroscopic characteristics
of this electron transport protein without requiring the classic rubredoxin
protein fold
Methylated Histidines Alter Tautomeric Preferences that Influence the Rates of Cu Nitrite Reductase Catalysis in Designed Peptides
No full textCopper proteins have the capacity
to serve as both redox active
catalysts and purely electron transfer centers. A longstanding question
in this field is how the function of histidine ligated Cu centers
are modulated by δ vs ε-nitrogen ligation of the imidazole.
Evaluating the impact of these coordination modes on structure and
function by comparative analysis of deposited crystal structures is
confounded by factors such as differing protein folds and disparate
secondary coordination spheres that make direct comparison of these
isomers difficult. Here, we present a series of de novo designed proteins
using the noncanonical amino acids 1-methyl-histidine and 3-methyl-histidine
to create Cu nitrite reductases where δ- or ε-nitrogen
ligation is enforced by the opposite nitrogen’s methylation
as a means of directly comparing these two ligation states in the
same protein fold. We find that ε-nitrogen ligation allows for
a better nitrite reduction catalyst, displaying 2 orders of magnitude
higher activity than the δ-nitrogen ligated construct. Methylation
of the δ nitrogen, combined with a secondary sphere mutation
we have previously published, has produced a new record for efficiency
within a homogeneous aqueous system, improving by 1 order of magnitude
the previously published most efficient construct. Furthermore, we
have measured Michaelis–Menten kinetics on these highly active
constructs, revealing that the remaining barriers to matching the
catalytic efficiency (kcat/KM) of native Cu nitrite reductase involve both substrate
binding (KM) and catalysis (kcat)
Taxonomy of the Proisotoma complex. Redefinition of genera and description of new species of Scutisotoma and Weberacantha (Collembola, Isotomidae)
No full textThe paper provides new information on morphological characters which are useful in generic diagnostics of the Proisotoma complex of Isotomidae. Based on this information, a number of known species are excluded from the redefined Proisotoma s. str. and moved to the genus Scutisotoma Bagnall, 1949, which is again given generic status. The following genera are given more precise definitions: Subisotoma Stach, 1947, Ballistura Borner, 1906, Proisotoma Borner, 1901 and Weberacantha Christiansen, 1951. A new genus, Strenzketoma, is erected for the species "Proisotoma" buddenbrocki Strenzke. Scutisotoma titusi (Folsom), S. muriphila (Grinbergs), and S. ladaki (Denis) are redescribed. Fourteen new species of the genus Scutisotoma (S. acorrelata sp. n., S. baica sp. n., S. dodecocellata sp. n., S. indigirka sp. n., S. karadagi sp. n., S. kolymica sp. n., S. longisensilla sp. n., S. matalini sp. n., S. millimetrica sp. n., S. montana sp. n., S. nicksmeti sp. n., S. schisti sp. n., S. stachanoremi sp. n., S. tenuidentifera sp. n.) and two new species of Weberacantha (W. echinodermata sp. n., W. magnomucrella sp. n.) are described. Types of S. ananevae ( Babenko & Bulavintsev), S. armeriae (Fjellberg), S. christianseni (Stach), S. oirota (Vilkamaa), S. stepposa (Martynova), S. tianshanica (Martynova), and S. tolerans (Babenko) have been studied. Keys to genera and to the known Holarctic species of Scutisotoma Bagnall and Weberacantha Christiansen are given
