A schistosome [beta] subunit remodels inactivation of a calcium channel _via_ an N-terminal polyacidic motif

The beta subunit of high voltage-activated Ca (Cav) channels targets the pore forming [alpha]~1~ subunit to the plasma membrane and defines the biophysical phenotype of the Cav channel complex. Cav channel inactivation following activation and opening is tightly regulated and is an essential property that not only prevents excessive entry of Ca^2+^ into the cell but may also have functions in signal transduction. The [beta] subunit modulates Ca^2+^-dependent and voltage-dependent components of Cav channel inactivation via its interaction with the I-II linker of the [alpha]~1~ subunit. Here, using Cav2.3 and whole-cell patch-clamp, we show that a [beta] subunit from the human parasite _Schistosoma mansoni_ ([beta]~Sm~) accelerates inactivation via a unique, long N-terminal polyacidic motif (NPAM). The accelerating effect of NPAM-containing subunits, both native ([beta]~Sm~)and chimeric mammalian [beta]~1b~, [beta]~2a~ and [beta]~3~ subunits to which NPAM had been attached, was only apparent when Ca^2+^ was internally buffered with BAPTA (5 mM) or when Ba^2+^ was used as the charge carrier, two commonly used strategies to eliminate Ca^2+^/calmodulin dependent inactivation. These results indicate that calmodulin is not involved. In addition to accelerating inactivation, NPAM-containing [beta] subunits significantly reduced current density with respect to their non NPAM-bearing counterparts. Interestingly, when the amino acids N terminal to NPAM were deleted, inactivation of Cav2.3 currents was faster than in the presence of the entire N-terminal portion of the [beta]~Sm~ subunit, as if the pre-NPAM region counteracts the effect of NPAM. Presence of NPAM also resulted in currents that activated faster, suggesting that NPAM increases open channel probability. However, NPAM does not modulate inactivation gating. In summary, this study identifies a structural determinant of Cav channel inactivation that is entirely unlike those previously known

APPLYING CHAID TO IDENTIFY THE ACCOUNTING-FINANCIAL CHARACTERISTICS OF THE MOST PROFITABLE REAL ESTATE COMPANIES IN SPAIN

The aim of this study is the determination, from an empirical perspective, of the accounting and financial features which could condition financial profitability of real estate companies, to identify the performances that guarantee its permanency in the current marketplace, characterized by the world economic crisis, specially in Spain, whose housing sector represents an important contributor to the economic growth. Although at a theoretical level the DuPont Model establishes the relationships between a group of accounting ratios and financial profitability. This paper uses a sample of 5,484 Spanish real estate companies to quantify these relationships and to extract the most relevant ones and to obtain the patterns of the most profitable companies. We use ROE to measure profitability and we analyze various independent variables about solvency, liquidity, activity, turnover, financial equilibrium and investment structure. The main contribution is of methodological nature, as we have applied statistics tools that do not require initial hypotheses on the distribution of the variables, by using a data mining technique of classification and regression tree based on rule induction algorithms known as CHAID. The study provides quantitatively success profiles by means of a set of rules describing the patterns of the most profitable companies.CHAID; financial profitability; classification trees; accounting ratios; Spain.

Impact of Equipment Failures and Wind Correlation on Generation Expansion Planning

Generation expansion planning has become a complex problem within a deregulated electricity market environment due to all the uncertainties affecting the profitability of a given investment. Current expansion models usually overlook some of these uncertainties in order to reduce the computational burden. In this paper, we raise a flag on the importance of both equipment failures (units and lines) and wind power correlation on generation expansion decisions. For this purpose, we use a bilevel stochastic optimization problem, which models the sequential and noncooperative game between the generating company (GENCO) and the system operator. The upper-level problem maximizes the GENCO's expected profit, while the lower-level problem simulates an hourly market-clearing procedure, through which LMPs are determined. The uncertainty pertaining to failures and wind power correlation are characterized by a scenario set, and their impact on generation expansion decisions are quantified and discussed for a 24-bus power system