Mechanistic insight into functionally different human islet polypeptide (hIAPP) amyloid: the intrinsic role of the C-terminal structural motifs

Targeting amyloidosis requires high-resolution insight into the underlying mechanisms of amyloid aggregation. The sequence-specific intrinsic properties of a peptide or protein largely govern the amyloidogenic propensity. Thus, it is essential to delineate the structural motifs that define the subsequent downstream amyloidogenic cascade of events. Additionally, it is important to understand the role played by extrinsic factors, such as temperature or sample agitation, in modulating the overall energy barrier that prompts divergent nucleation events. Consequently, these changes can affect the fibrillation kinetics, resulting in structurally and functionally distinct amyloidogenic conformers associated with disease pathogenesis. Here, we have focused on human Islet Polypeptide (hIAPP) amyloidogenesis for the full-length peptide along with its N- and C-terminal fragments, under different temperatures and sample agitation conditions. This helped us to gain a comprehensive understanding of the intrinsic role of specific functional epitopes in the primary structure of the peptide that regulates amyloidogenesis and subsequent cytotoxicity. Intriguingly, our study involving an array of biophysical experiments and ex vivo data suggests a direct influence of external changes on the C-terminal fibrillating sequence. Furthermore, the observations indicate a possible collaborative role of this segment in nucleating hIAPP amyloidogenesis in a physiological scenario, thus making it a potential target for future therapeutic interventions

Neutrophil Extracellular Trap–Derived Enzymes Oxidize High‐Density Lipoprotein: An Additional Proatherogenic Mechanism in Systemic Lupus Erythematosus

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108351/1/art38703.pd

Spawning Seasonality of Major Fishery Groups Along Tamil Nadu-Andhra Pradesh Coast

Available information on the spawning season of finfishes, crustaceans and cephalopods along the Tamil Nadu-Andhra Pradesh coast indicate prolonged spawning of most of the groups. Maximum number of species (41) spawn during January. Considering the spawning intensity and catch rate of trawlers, it is suggested that trawl operation may be banned in April and during Novermber-December dong the Tamil Nadu-Andhra Pradesh coast

Expression, purification and characterization of C2 domain of milk fat globule-EGF-factor 8-L

Milk fat globule-EGF-factor 8-L (MFG-E8L) is secreted by activated macrophages and functions as a linker protein or opsonin between the dying cells and phagocytes. MFG-E8L recognizes the apoptotic or dying cells by specifically binding to Phosphatidylserine (PS) exposed on the outer cell surface and enhances the engulfment of the apoptotic cells by phagocytes, thereby preventing the inflam¬mation and autoimmune response against intracellular antigens that can be released from the dying cells. MFG-E8L contains two EGF¬like domains, P/T (proline/threonine) rich domain followed by two discoidin-like domains (C1 and C2). Recent studies have shown that the C2 domain of MFG-E8L is specifically involved in interaction with PS exposed on the apoptotic cells. Towards understanding this specific molecular interaction between the MFG-E8L C2 domain and PS, we expressed, purified the C2 domain of MFG-E8L and per¬formed the binding studies with phospholipids by 31P NMR experiment. We demonstrated that our recombinant construct and expres¬sion system were effective and allowed us to obtain the C2 domain and also showed that the purified C2 domain was stable and properly folded, and our 31P NMR studies indicated that the C2 domain had specific binding with PS.Accepted versio

Design of β-hairpin peptides for modulation of cell adhesion by β-turn constraint

The CD2−CD58 interaction in immune regulation and disease pathology has provided new targets for developing potential immunosuppressive agents. In the present study, we report the introduction of constraints to generate β-hairpin structures from the strand sequences of CD2 protein. The β-hairpin structures were induced in the designed peptides by introducing Pro-Gly sequences in the peptides. Results from NMR and MD simulation indicated that the peptides exhibited β-turn structure at the X-Pro-Gly-Y sequence and formed the β-hairpin structure in solution. The ability of these peptides to inhibit cell adhesion was evaluated by two cell adhesion assays. Among the peptides studied (1−4) (P1−P4), peptides 2−4 were able to inhibit cell adhesion between Jurkat cells and SRBC nearly 50% at 180 μM, and 80% inhibition between Jurkat cells and Caco-2 cells was seen at 90 μM. Peptide 1 did not show significant inhibition activity compared to control

1H, 13C, and 15N resonance assignments of subunit F of the A1AO ATP synthase from Methanosarcina mazei Gö1

Energy coupling between the A1 ATPase of archaea type A1AO ATP synthase and its integral membrane sub-complex AO occurs via the stalk part, formed by the subunits C, D and F. To provide a molecular basis of the energy coupling, we performed NMR studies. Here, we report the assignment of the subunit F.Accepted versio

NMR solution structure of subunit F of the methanogenic A1AO adenosine triphosphate synthase and its interaction with the nucleotide-binding subunit B

The A1AO adenosine triphosphate (ATP) synthase from archaea uses the ion gradients generated across the membrane sector (AO) to synthesize ATP in the A3B3 domain of the A1 sector. The energy coupling between the two active domains occurs via the so-called stalk part(s), to which the 12 kDa subunit F does belong. Here, we present the solution structure of the F subunit of the A1AO ATP synthase from Methanosarcina mazei Gö1. Subunit F exhibits a distinct two-domain structure, with the N-terminal having 78 residues and residues 79−101 forming the flexible C-terminal part. The well-ordered N-terminal domain is composed of a four-stranded parallel β-sheet structure and three α-helices placed alternately. The two domains are loosely associated with more flexibility relative to each other. The flexibility of the C-terminal domain is further confirmed by dynamics studies. In addition, the affinity of binding of mutant subunit F, with a substitution of Trp100 against Tyr and Ile at the very C-terminal end, to the nucleotide-binding subunit B was determined quantitatively using the fluorescence signals of natural subunit B (Trp430). Finally, the arrangement of subunit F within the complex is presented

Solution Structure, Determined by Nuclear Magnetic Resonance, of the b30-82 Domain of Subunit b of Escherichia coli F1Fo ATP Synthase ▿

Subunit b, the peripheral stalk of bacterial F1Fo ATP synthases, is composed of a membrane-spanning and a soluble part. The soluble part is divided into tether, dimerization, and δ-binding domains. The first solution structure of b30-82, including the tether region and part of the dimerization domain, has been solved by nuclear magnetic resonance, revealing an α-helix between residues 39 and 72. In the solution structure, b30-82 has a length of 48.07 Å. The surface charge distribution of b30-82 shows one side with a hydrophobic surface pattern, formed by alanine residues. Alanine residues 61, 68, 70, and 72 were replaced by single cysteines in the soluble part of subunit b, b22-156. The cysteines at positions 61, 68, and 72 showed disulfide formation. In contrast, no cross-link could be formed for the A70C mutant. The patterns of disulfide bonding, together with the circular dichroism spectroscopy data, are indicative of an adjacent arrangement of residues 61, 68, and 72 in both α-helices in b22-156