Solution structure of the motile major sperm protein (MSP) of Ascaris suum - evidence for two manganese binding sites and the possible role of divalent cations in filament formation 1 1Edited by P. E. Wright

1998 ◽  
Vol 284 (5) ◽  
pp. 1611-1624 ◽  
Author(s):  
Andreas Haaf ◽  
Lawrence LeClaire ◽  
Gregory Roberts ◽  
Helen M. Kent ◽  
Thomas M. Roberts ◽  
...  
Keyword(s):  
Binding Sites ◽  
Solution Structure ◽  
Divalent Cations ◽  
Ascaris Suum ◽  
Major Sperm Protein ◽  
Filament Formation ◽  
Sperm Protein

Supramolecular assemblies of the Ascaris suum major sperm protein (MSP) associated with amoeboid cell motility

1994 ◽  
Vol 107 (10) ◽  
pp. 2941-2949
Author(s):  
K.L. King ◽  
M. Stewart ◽  
T.M. Roberts
Keyword(s):  
Ascaris Suum ◽  
Leading Edge ◽  
Intrinsic Property ◽  
Basic Unit ◽  
Major Sperm Protein ◽  
Sperm Protein ◽  
Amoeboid Cell ◽  
Left Handed ◽  
Self Association

Sperm of the nematode, Ascaris suum, are amoeboid cells that do not require actin or myosin to crawl over solid substrata. In these cells, the role usually played by actin has been taken over by major sperm protein (MSP), which assembles into filaments that pack the sperm pseudopod. These MSP filaments are organized into multi-filament arrays called fiber complexes that flow centripetally from the leading edge of the pseudopod to the cell body in a pattern that is intimately associated with motility. We have characterized structurally a hierarchy of helical assemblies formed by MSP. The basic unit of the MSP cytoskeleton is a filament formed by two subfilaments coiled around one another along right-handed helical tracks. In vitro, higher-order assemblies (macrofibers) are formed by MSP filaments that coil around one another in a left-handed helical sense. The multi-filament assemblies formed by MSP in vitro are strikingly similar to the fiber complexes that characterize the sperm cytoskeleton. Thus, self-association is an intrinsic property of MSP filaments that distinguishes these fibers from actin filaments. The results obtained with MSP help clarify the roles of different aspects of the actin cytoskeleton in the generation of locomotion and, in particular, emphasize the contributions made by vectorial assembly and filament bundling.

Extracellular Calcium And Platelets

1981 ◽  
Author(s):  
P M Taylor ◽  
S Heptinstall
Keyword(s):  
Divalent Cation ◽  
Binding Sites ◽  
Divalent Cations ◽  
Extracellular Calcium ◽  
Time Dependent ◽  
Aggregation Process ◽  
Platelet Surface ◽  
Intracellular Pool ◽  
Continuous Movement

To gain more information on the role of extracellular Ca in platelet behaviour, the movement of 45Ca between plasma and platelets has been studied. Ttoo experimental procedures have been used: platelets were either studied in plasma that contained near-physiological levels of divalent cations or were studied in divalent cation-depleted plasma.There was a continuous movement of Ca from plasma into platelets when the latter were suspended in plasma that contained near-physiological levels of divalent cations. The iptake was linear with time (2.0 to 2.5 ng ion Ca/109 platelets/60 mins) and was faster at 37°C than at 25°C. The amount of Ca taken up by the platelets increased as the extracellular Ca level was increased and was markedly inhibited by Mg. Sr did not affect the uptake. EGTA displaced only a small amount of the Ca that associated with the plater lets which indicated that Ca was taken up into an intracellular pool rather than sinply bound to the platelet surface. The relevance of this movement of Ca into the cells to platelet behaviour has not been established.Studies using platelets suspended in divalent cation- depleted plasma shewed that extracellular Ca was in equilibrium with Ca bound at or near the platelet surface. The binding of Ca was time-dependent but saturable (0.30 to 0.50 ng ion Ca/109 platelets/30 mins), and the majority was readily displaced by EGTA. The amount of Ca bound to the cells increased as the extracellular Ca level was increased but was little affected by an excess of either Mg or Sr. Mare Ca bound to platelets when they were incubated at 25°C than at 37°C. This was because platelets lost their ability to bind Ca when they were incubated at 37°C in divalent cation-depleted plasma. This phenomenon was time-dependent and irreversible and was paralleled by a loss in the ability of the platelets to aggregate. These Ca binding sites would seem to be relevant to the aggregation process.

Crystallization of the Motile Major Sperm Protein (MSP) of the Nematode Ascaris suum

1993 ◽  
Vol 232 (1) ◽  
pp. 298-300 ◽  
Author(s):  
Murray Stewart ◽  
Karen L. King ◽  
Thomas M. Roberts
Keyword(s):  
Ascaris Suum ◽  
Major Sperm Protein ◽  
Sperm Protein

scholarly journals The conserved molting/circadian rhythm regulator NHR-23/NR1F1 serves as an essential co-regulator of C. elegans spermatogenesis

Development ◽  
2020 ◽  
Vol 147 (22) ◽  
pp. dev193862
Author(s):  
James Matthew Ragle ◽  
Abigail L. Aita ◽  
Kayleigh N. Morrison ◽  
Raquel Martinez-Mendez ◽  
Hannah N. Saeger ◽  
...  
Keyword(s):  
Regulatory Network ◽  
Nuclear Hormone Receptor ◽  
Model Systems ◽  
Residual Body ◽  
Major Sperm Protein ◽  
Sperm Protein ◽  
C Elegans ◽  
Gene Regulatory ◽  
Established Role

ABSTRACTIn sexually reproducing metazoans, spermatogenesis is the process by which uncommitted germ cells give rise to haploid sperm. Work in model systems has revealed mechanisms controlling commitment to the sperm fate, but how this fate is subsequently executed remains less clear. While studying the well-established role of the conserved nuclear hormone receptor transcription factor, NHR-23/NR1F1, in regulating C. elegans molting, we discovered that NHR-23/NR1F1 is also constitutively expressed in developing primary spermatocytes and is a critical regulator of spermatogenesis. In this novel role, NHR-23/NR1F1 functions downstream of the canonical sex-determination pathway. Degron-mediated depletion of NHR-23/NR1F1 within hermaphrodite or male germlines causes sterility due to an absence of functional sperm, as depleted animals produce arrested primary spermatocytes rather than haploid sperm. These spermatocytes arrest in prometaphase I and fail to either progress to anaphase or attempt spermatid-residual body partitioning. They make sperm-specific membranous organelles but fail to assemble their major sperm protein into fibrous bodies. NHR-23/NR1F1 appears to function independently of the known SPE-44 gene regulatory network, revealing the existence of an NHR-23/NR1F1-mediated module that regulates the spermatogenesis program.

scholarly journals Functional roles of Mg2+ binding sites in ion-dependent gating of a Mg2+ channel, MgtE, revealed by solution NMR

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Tatsuro Maruyama ◽  
Shunsuke Imai ◽  
Tsukasa Kusakizako ◽  
Motoyuki Hattori ◽  
Ryuichiro Ishitani ◽  
...  
Keyword(s):  
Binding Sites ◽  
Divalent Cations ◽  
Solution Nmr ◽  
Resonance Spectroscopy ◽  
Wild Type ◽  
Cellular Functions ◽  
Functional Roles ◽  
Structure And Dynamics ◽  
Mutant Forms

Magnesium ions (Mg2+) are divalent cations essential for various cellular functions. Mg2+ homeostasis is maintained through Mg2+ channels such as MgtE, a prokaryotic Mg2+ channel whose gating is regulated by intracellular Mg2+ levels. Our previous crystal structure of MgtE in the Mg2+-bound, closed state revealed the existence of seven crystallographically-independent Mg2+-binding sites, Mg1–Mg7. The role of Mg2+-binding to each site in channel closure remains unknown. Here, we investigated Mg2+-dependent changes in the structure and dynamics of MgtE using nuclear magnetic resonance spectroscopy. Mg2+-titration experiments, using wild-type and mutant forms of MgtE, revealed that the Mg2+ binding sites Mg1, Mg2, Mg3, and Mg6, exhibited cooperativity and a higher affinity for Mg2+, enabling the remaining Mg2+ binding sites, Mg4, Mg5, and Mg7, to play important roles in channel closure. This study revealed the role of each Mg2+-binding site in MgtE gating, underlying the mechanism of cellular Mg2+ homeostasis.

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